2ndinternational workshop on magnonics

2nd

International Workshop

on Magnonics:

From Fundamentals to Applications

Program and Abstract Book

Recife, PE, Brazil – August 7-10, 2011

2

www.hotelarmacao.com.br

http://www.hotelarmacao.com.br/


3

2nd International Workshop on

Magnonics

Recife, PE, Brazil – August 7-10, 2011

The evolution in the understanding of the dynamics of the magnetization has traditionally offered technological solutions for processing and storage of information in a variety of applications. In recent times the ability to tailor the properties of magnetic materials on the nanoscale has raised the possibilities of developing magnetic field controlled devices in which spin waves (magnons) are used to carry and process information. In addition, new dynamic phenomena have been discovered in traditional materials which allow the interconversion between electric and spin signals, such as the spin Hall and related effects, which widens the possibilities of the role of magnons in spintronics. The 2

nd edition of the Workshop on Magnonics

intends to bring together scientists and engineers interested in recent developments in studies ranging from fundamental magnonic properties to their application in the information technologies. The principal objective of the Workshop is to consolidate the efforts of researchers working in the field of magnonics in order to work out new concepts leading to practical realization of magnonic devices. Future challenges for magnonics will be identified, which will motivate younger researchers to follow the new pathways and perspectives.

The first Workshop on Magnonics: From Fundamentals to Applications took place in Dresden, Germany on August 2 - 7, 2009. At that time the organizers suggested that the “Magnonics Community” should continue effort to organize the Workshop every two years. As an effort of several people, the 2nd Workshop on Magnonics will take place in the resort city of Porto de Galinhas (http://hotelarmacao.com.br/en/), near Recife, the capital of the state of Pernambuco, located in the northeast coast of Brazil, on August 7 – 10, 2011.

http://hotelarmacao.com.br/en/

2nd

Workshop on Magnonics. August 7-10, 2011 - Recife, PE Brazil

4

Organizing committee

Andrei Slavin

Department of Physics Oakland University Rochester, Michigan 48309, USA

Antonio Azevedo Departamento de Física Universidade Federal de Pernambuco 50670-901, Recife, PE Brazil

José C. Egues Instituto de Física de São Carlos

Universidade de São Paulo 13566-590, São Carlos, SP Brazil

Roberto B. Muniz Instituto de Fisica

Universidade Federal Fluminense 24210-346, Niteroi, RJ Brazil

Rubem L. Sommer Centro Brasileiro de Pesquisas Físicas Rua Dr. Xavier Sigaud 150, Urca 22290-180 Rio de Janeiro RJ, Brazil

Samuel D. Bader Materials Science Division

Argonne National Laboratory Argonne, Illinois 60439, USA

Sang-Koog Kim Research Center for Spin Dynamics and Spin-Wave Devices, Nanospinics Laboratory, Department of Materials Science and Engineering, Seoul National University, Seoul 151-744, South Korea.

Sergei A. Nikitov Institute of Radioengineering and Electronics

Russian Academy of Sciences 11 Mokhovaya Street, 103907 Moscow, Russia

Sergej O. Demokritov Institute for Applied Physics University of Muenster, Corrensstraße 2-4 48149 Muenster, Germany

Sergio M. Rezende Departamento de Física Universidade Federal de Pernambuco 50670-901, Recife, PE Brazil


5

Invited Speakers

Plenary talk Professor Dr. Sadamichi Maekawa

Advanced Science Research Center (ASRC) Japan Atomic Energy Agency (JAEA) Tokai 319-1195 Japan

Oral presentations Professor Johan Akerman

Department of Physics, University of Gothenburg

412 96 Gothenburg, SWEDEN. Professor Zbigniew Celinski

Department of Physics and Energy Science 1420 Austin Bluffs Parkway, Room Colorado Springs CO 80918 USA Dr. Vladislav E. Demidov

Institut fuer Angewandte Physik Westfaelische Wilhelms-Universitaet Muenster Corrensstr. 2-4 - 48149 Muenster, Germany Dr. Grégoire de Boulens

Service de Physique de l‟État Condensé CNRS URA 2464, CEA Saclay 91191 Gif-sur-Yvette, France Dr. Ursula Ebels

CEA/DSM/INAC/SPINTEC/SPINTEC 17 rue des martyrs 38054 Grenoble, France Dr. Yuri K. Fetisov

Moscow Institute of Radioengineering, Electronics and Automation (MIREA) 117454 Moscow, Russia Dr. Yu. A. Filimonov

Institute of Radioengineering and Electronics, Russian Academy of Sciences, Saratov Branch, 410720 Saratov, Russia Dr. Julie Grolier

Unité Mixte de Physique CNRS/Thales (UMR137) 1 Avenue A. Fresnel, 91767 Palaiseau Cedex, France

Professor Dr. Dirk Grundler

Physik-Department E10 Fakultät für Physik, Technische Universität München James-Franck-Straße 1

D-85747 Garching Germany Professor Gianluca Gubbiotti

CNISM Unità di Perugia Dipartimento di Fisica, Universit`a di Perugia Via Pascoli, I-06123 Perugia, Italy

2nd


6

Professor Bret Heinrich

Department of Physics, Simon Fraser University Burnaby, British Columbia, V5A 1S6, Canada Professor Robert J. Hicken

School of Physics University of Exeter Exeter EX4 4QL, United Kingdom

Professor Dr. Burkard Hillebrands

Fachbereich Physik, Technische Universitaet Kaiserslautern Erwin-Schroedinger-Strasse 56

67663 Kaiserslautern, Germany

Professor Boris Kalinikos

Department of Physical Electronics and Technology St.Petersburg Electrotechnical University 197376, St. Petersburg, Russia

Dr. Andrei I. Kirilyuk

Institute for Molecules and Materials Radboud University Nijmegen Heyendaalseweg 135 6525 AJ Nijmegen, The Netherlands

Professor Dr. Juergen Kirschner

Max-Planck-Institut für Mikrostrukturphysik Experimental Department 1 Weinberg 2 06120 Halle Germany

Professor Ilya Krivorotov

University of California, Irvine 310E Rowland Hall Irvine, CA 92697 Dr. Volodymyr V. Kruglyak

Advanced Research Fellow

School of Physics, University of Exeter Stocker Road Exeter, EX4 4QL

Dr. Robert D. McMichael

Metallurgy Division, NIST 100 Bureau Drive, Gaithersburg, Maryland USA

Professor G.A. Melkov

13 Bubnova Str. app.134 Kiev 03040 UKRAINE. Professor Douglas L. Mills

Department of Physics and Astronomy

University of California Irvine, California 92697, USA

Professor Dr. Markus Müenzenberg

Georg-August-University Goettingen, I. Phys. Institut, 37077 Goettingen,Germany


7

Professor Shuichi Murakami

Tokyo Institute of Technology 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551, Japan Dr. Valentyn Novosad

Materials Science Division; Bldg. 223 Argonne National Laboratory 9700 South Cass Ave. Argonne, IL 60439 Professor Sergio M. Rezende

Departamento de Física Universidade Federal de Pernambuco 50670-901, Recife, PE Brazil

Dr. Oleksandr Serga

Fachbereich Physik, TU Kaiserslautern Erwin-Schroedinger-Strasse 56 67663 Kaiserslautern, Germany

Professor Mingzhong Wu

Department of Physics, Colorado State University Fort Collins, Colorado 80523, USA

Program Table

Aug 07, 2011

(Sunday)

Aug 08, 2011

(Monday)

Aug 09, 2011

(Tuesday)

Aug 10, 2011

(Wednesday)

Magnonic

excitations in

nanomagnets I

(Chairperson:

Muniz)

Magnonic

crystals II

(Chairperson:

Sommer)

Novel materials

and

phenomena

(Chairperson:

Arias)

09:00 -

09:30 Mills Grundler Kalinikos

09:30 -

10:00 De Loubens Gubiotti Celinski

10:00 -

10:30 Hicken Kruglyak Fetisov

10:30 -

11:00 Coffee break Coffee break Coffee break

Magnonic

crystals I

(Chairperson:

Nikitov)

Magnonic

excitations in

nanomagnets II

(Chairperson:

Egues)

Magnon

caloritronics

(Chairperson:

Azevedo)

11:00 -

11:30 Melkov Heinrich Krivorotov

11:30 -

12:00 Filimonov Murakami Rezende

12:00 -

14:00 Lunch Lunch Lunch

Spin-wave

phenomena

and devices I

(Chairperson:

Demokritov)

13:50-14:00

Group

photography

Spin transfer

nano-

oscillators

(Chairperson:

Sang-Koog

Kim)

14:00 -

14:30 Serga

Poster session

Grolier

14:30 -

15:00 Wu Ebels

15:00 -

15:30 Kirschner Akerman

15:30 -

16:00 Coffee break Coffee break

Spin-wave

phenomena

and devices II

(Chairperson:

Slavin)

Magnon

spintronics

(Chairperson:

Rezende)

16:00 -

16:30 Kirilyuk Demidov

16:30 -

17:00 Novosad

Free

McMichael

17:00 -

17:30 Opening Münzenberg Hillebrands

17:30 -

18:30 Maekawa Poster session

Closing 18:30 -

20:30

Welcome

Cocktail Free


9

Contents

Abstract pages

Plenary talk

Sunday, 18:00 – 19:00

Non-equilibrium magnons, spin current and spin Seebeck

effect

Sadamichi Maekawa.......................................................................................16

Invited talks

Monday, August 8 Session: Magnonic excitations in nanomagnets I

Monday, 9:00 – 9:30

Spin excitations and spin relaxation in subnanoscale

ferromagnets

Douglas L. Mills………………………………..…….……………….……………17 Monday, 9:30 – 10:00

Identification and selection rules of the spin-wave eigen-

modes in a normally magnetized nano-pillar

Grégoire de Loubens………………………………………….…………………..17

Monday, 10:00 – 10:30

Bottom up magnonics: dipolar interaction of a pair of

nanoscale magnetic disks

Robert J. Hicken……………………………………………….…………………..18 Session: Magnonic crystals I

Monday, 11:00 – 11:30

Nonlinear magnonic crystal based on a planar array of

magnetic dots

Gennadii Melkov.............................................................................................19 Monday, 11:30 – 12:00

Spin-wave excitations in magnonic crystals

Yuri Filimonov.................................................................................................20 Session: Spin-wave phenomena and devices

Monday, 14:00 – 14:30

Magnon gases and condensates

Alexander Serga.............................................................................................20

Monday, 14:30 – 15:00

Manipulation of spin waves in yttrium iron garnet thin films

through Interfacial spin scattering

Mingzhong Wu................................................................................................21

Monday, 15:00 – 15:30

Magnon and phonon excitation at the Fe(100)/O surface by

scattering of spin-polarized electrons

Juergen Kirschner...........................................................................................22

2nd


10

Monday, 16:00 – 16:30

The role of angular momentum in ultrafast magnetization

dynamics

Andrei Kirilyuk.................................................................................................22

Monday, 16:30 – 17:00

Dynamics of spin vortices: from physics to cancer therapy

Valentyn Novosad...........................................................................................23

Monday, 17:00 – 17:30

Photo-magnonics

Markus Münzenberg............................ .................... ...... ...............................24

Tuesday, August 9 Session: Magnonic crystals II

Tuesday, 9:00 – 9:30

Spin wave propagation in magnonic crystals made from

nanopatterned permalloy

Dirk Grundler……………………………………….……..…………..……………25 Tuesday, 9:30 – 10:00

Controlling spin wave propagation in planar magnonic crystal

Gianluca Gubbiotti………………………………………..………………………..26 Tuesday, 10:00 – 10:30

Magnonics beyond magnonic crystals: magnonic meta-

materials and devices

Volodymyr Kruglyak……………….……………………………………………....26 Session: Magnonic excitations in nanomagnets II.

Tuesday, 11:00 – 11:30

Spin pumping at ferromagnet (Fe,YIG)/normal metal (Au,Ag)

interfaces and spin transport in Au and Ag films

Bret Heinrich……………………….………………………………………………27 Tuesday, 11:30 – 12:00

Theory of rotations of magnon wavepacket and magnon Hall

effect

Shuichi Murakami……………………….…………..………………..…………...28 Wednesday, August 10 Session: Novel materials and phenomena

Wednesday, 9:00 – 9:30

Microwave phenomena in planar ferrite-ferroelectric

heterostructures: theory and applications

Boris Kalinikos………………………………….…………...….………………….29 Wednesday, 9:30 – 10:00

Magnetic materials for on-wafer microwave devices

Zbigniew Celinski………………………….……………………………………….29 Wednesday, 10:00 – 10:30

Microwave magnetoelectric interactions in multiferroic

structures and novel devices

Yuri Fetisov ………………………………….……………..…..………………….30


11

Session: Magnon caloritronics

Wednesday, 11:00 – 11:30

Thermally-assisted nonlinear dynamics of a nanomagnet

excited by spin transfer torque

Ilya Krivorotov ……….……………..……………………..……………………….31

Wednesday, 11:30 – 12:00

Amplification of Spin Waves by the Spin Seebeck Effect

Sergio M. Rezende….…………….….…………..……………………………….31 Session: Spin transfer nano-oscillators

Wednesday, 14:00 – 14:30

Spin transfer dynamics in vortex based oscillators

Julie Grollier …………………………………………………....…………………32 Wednesday, 14:30 – 15:00

Analysis of non-linear parameters of spin torque driven

excitations

Ursula Ebels ……………………….……….………………..….…………………33 Wednesday, 15:00 – 15:30

Nano-contact spin torque oscillator based magnonic building

blocks

Johan Åkerman …………………….………………………………....…………..34

Session: Magnon spintronics

Wednesday, 16:00 – 16:30

Control of spin-wave emission characteristics of spin-torque

nano-oscillators

Vladislav Demidov ……………………………………………...….……………..34 Wednesday, 16:30 – 17:00

Using magnons to probe spintronic materials properties

Robert McMichael …………………………………..……………………………..35 Wednesday, 17:00 – 17:30

Magnon Spintronics

Burkard Hillebrands ……………………………………………………….……...36

2nd


12

Poster Session

P1. Spin current absorption in thin metal films measured

through ferromagnetic resonance

A. Ghosh, S. Auffret, U. Ebels, and W. E. Bailey...........................................37

P2. Vortex dynamics in magnetic disks

Alexandre M. Gonçalves, Naiara Y. Klein, and Luiz C. Sampaio....................38

P3. Spin-electromagnetic wave ferrite-ferroelectric nonlinear

phase shifters

Alexey Ustinov, and Boris Kalinikos…………………………………………….38

P4. The dynamic magnonic crystal: a window into new wave

phenomena

Alexy D. Karenowska, Andrii V. Chumak, Vasil S. Tiberkevich, Alexander A. Serga, John F. Gregg, Andrei N. Slavin, and Burkard Hillebrands…..……….39

P5. Generation of Dark and Bright Spin Wave Envelope Soliton

Trains Through Self-Modulation Instability in Magnonic

Crystals

Andrey Drozdovskii, Alexey Ustinov, and Boris Kalinikos……………..………40

P6. Photo-magnonics: Spin-wave localization in magnonic

crystals

Benjamin Lenk, Fabian Garbs, Henning Ulrichs, and Markus Münzenberg…41

P7. Magnetization Dynamics of Ni81Fe19/Cu Films

Electrodeposited on Copper Microwire

B. G. Silva, D. E. González-Chávez, J. Gomes Filho, and R. L. Sommer......41

P8. Terahertz Band Gaps in Generalized Fibonacci

Quasiperiodic Magnonic Crystals

Carlos H. O. Costa, Manoel S. Vasconcelos and Eudenilson L. Albuquerque....................................................................................................42

P9. Schottky Barrier in ZnO Electrodepotited on Pt and Ni

Films

Carolina F. Cerqueira and Luiz C. Sampaio...................................................43

P10. Large Area Molecularly Assembled Nanopatterns for

Devices (LAMAND)

Claudia Simao, Achille Francone, Nikolaos Kehagias, Richard A. Farrell, Marc Zelsmann, Mustapha Chouiki, Rainer Schoeftner, Vincent Reboud, Justin D. Holmes, Michael A. Morris, and Clivia Sotomayor Torres….......…43

P11. Magnetization dynamics of Py/Ag multilayered films

studied with vector network analyzer magnetometry

D.E. González-Chávez, T. L. Marcondes, M.A. Corrêa, A. M. H. de Andrade, and R. L. Sommer...........................................................................................45

P12. Low-temperature spectroscopy on magnonic devices in

perpendicular fields

T. Schwarze, F. Brandl, R. Huber, G. Duerr, S. Neusser, and Dirk Grundler…...............................................................................................45


13

P13. Properties of magnetic nanodots with perpendicular

anisotropy

Erico Novais, Pedro Landeros, Andreia Barbosa, Maximiliano Martins, Flavio Garcia, and Alberto Guimarães.......................................................................46

P14. Exploration of spin-wave Bloch modes in hexagonal

lattices with low damping

Fabian Garbs, Benjamin Lenk, and Markus Münzenberg………. ..….……….46

P15. Standing spin waves in NiFe/FeMn/NiFe exchange-biased

asymmetrical trilayers

Fernando Pelegrini, Valberto P. Nascimento, Armando Biondo, Edson C. Passamani, and Elisa Baggio Saitovitch.........................................................47

P16. Graphene-based spin current waveguides: a theoretical

framework

Filipe S. M. Guimarães…………………………………………………….……...47

P17. Spin waves in antidot lattices on suspended membranes

Florian Brandl, Rupert Huber, Sebastian Neusser, Georg Dürr, and Dirk Grundler………………………………………..…………………………..…48

P18. Spin current injection by spin Seebeck and spin pumping

effects in YIG/Pt structures

Gilvânia L. da Silva, L.H. Vilela-Leão, S. M. Rezende, and A. Azevedo.........48

P19. Spatial profile of both thermal and pumped spin waves in

magnetic nanostructures investigated by micro-focused P20.

Brillouin light scattering

Giovanni Carlotti, Gianluca Gubbiotti, Marco Madami, and Silvia Tacchi.......49

P20. Spin Wave Propagation in Thin Micron-sized Permalloy

Stripes

Hans Bauer, Georg Woltersdorf, and Christian Back……….……..…………..50

P21. Tailoring Magnetization Dynamics at Nanoscale

Igor Barsukov, Y. Fu, A. Rubacheva, F. Römer, R. Meckenstock, J. Lindner, and M. Farle....................................................................................................50

P22. Static and dynamic properties of magnetic vortices in

small disks

Jeovani Brandão, Naiara Y. Klein, and Luiz C. Sampaio................................51

P23. All-optical investigation of propagating and standing spin

waves in magnetic micro-waveguides

Katrin Vogt, Helmut Schultheiss, Philipp Pirro, and Burkard Hillebrands.......51

P24. Magnons in Ultrathin Fe films: The Influence of the

Dzyaloshinskii-Moriya Interaction

Kh. Zakeri, Y. Zhang, J. Prokop, T.-H. Chuang, W.Tang, and J. Kirschner…52

P.25 Tailoring Spin Dynamics by Magnetic Nanopatterning

Using Ion Irradiation

Kilian Lenz, Michael Körner, Anja Banholzer, Maciej Oskar Liedke, Jochen Grebing, Jeffrey McCord, and Jürgen Fassbender …………………….……53

P26. Unidirectional anisotropy in the spin pumping voltage in

YIG/Pt bilayers

L. H. Vilela-Leão, C. Salvador, A. Azevedo, and S. M. Rezende....................53

2nd


14

P27. Topological magnetic structures in Mn corrals on Pt(111)

surface

Marcelo Ribeiro, Gregório B. CorrêaJr, Anders Bergman, Lars Nordström, Olle Eriksson, and Angela Klautau ………………..…..………………………...54

P28. Dipolar-glass behavior of an amorphous insulating film

containing Fe particles

Martin J.Zuckermann, and Norberto Majlis……….………………………...…..55

P29. Broadband FMR studies in Nanocrystalline films

M. J. P. Alves, J. Gomes Filho, D. E. González Chavez, T. L. Marcondes, and R. L. Sommer..................................................................................................55

P30. Injection locking of tunnel junction oscillators to a

microwave current

M. Quinsat, J. F. Sierra, I. Firastrau, V. Tiberkevich, A. Slavin, D. Gusakova,

L. D. Buda-Prejbeanu, M. Zarudniev, J.-P. Michel, U. Ebels, B. Dieny, M.-C. Cyrille,

J. A. Katine, D. Mauri, and A. Zeltser…………..………….……..…….55

P31. Spin wave resonance in exchange-biased NiFe/IrMn

bilayers

M. A. Sousa, F. Pelegrini, J. Q. Marcatoma, W. Alayo, and E. Baggio- Saitovitch.........................................................................................................56

P32. Electric and magnetic tunability of multiferroic magnonic

crystal

Natalia Grigoryeva, and Boris Kalinikos…………..……………………………..57

P33. Direct Observation of First Order Quantum Coherence

and Phase Locking in Magnon Bose-Einstein Condensate

P. Nowik-Boltyk, O. Dzyapko, V. E. Demidov, and S. O. Demokritov........….57

P34. Tailoring magnetic relaxation in thin films with different

defects features

P. Landeros, R. E. Arias, and D. L. Mills……………….…………….………….58

P35. Dymanic magnetization studies in NiFe/IrMn/Ta exchange

biased

R. Dutra, D. E. Gonzàlez-Chávez, A. M. H. de Andrade, and R. L. Sommer...........................................................................................................58

P36. Tuning misalignment of ferromagnetic and

antiferromagnetic easy axes in exchange biased bilayers

R. L. Rodríguez-Suárez, L. H. Vilela- Leão, T. Bueno, J. B. S. Mendes, P. Landeros, Hernandez E. P, S. M. Rezende, and A. Azevedo....................59

P37. Josephson Effect in Bose-Einstein Condensate of

Magnons at Room Temperature

Roberto Troncoso and Alvaro S. Nuñez .......................................................59

P38. Magnetostatic band gaps in geometrically modulated thin

films

Claudio Jarufe and Rodrigo Arias...................................................................60

P39. Spin-wave propagation through a reprogrammable one-

dimensional magnonic crystal

Rupert Huber, Sebastian Neusser, Georg Dürr, Thomas Schwarze, and Dirk

Grundler..........................................................................................................60


15

P40. Energy transfer between vortex-state magnetic disks by

stimulated vortex gyration

Hyunsung Jung, Ki-Suk Lee, Dae-Eun Jeong, Youn-Seok Choi, Young-Sang Yu, Dong-Soo Han, Andreas Vogel, Lars Bocklage, Guido Meier, Mi-Young Im, Peter Fisher, and Sang-Koog Kim ..........................................................61

P41. Vortex gyratons in magnonic cystals of dipolar coupled

magnetic nanodisks

Dong-Soo Han, Dae-Eun Jeong, and Sang-Koog Kim .................................62

2nd


16

Plenary Talk

Sunday, 18:00 – 19:00

Non-equilibrium magnons, spin current and spin Seebeck

effect

Sadamichi Maekawa

Advanced Science Research Center, Japan Atomic Energy Agency.

Non-equilibrium magnons in a ferromagnet carry the spin current [1]. When the magnons are generated by the electric voltage via the s-d exchange interaction, the resulting spin current transmits the electric signal in the

ferromagnet [2]. On the other hand, when they are generated by heat, the spin current carries the thermal energy. This is called the Spin Seebeck effect [3]. Here, we formulate the spin current in a ferromagnetic insulator generated by electric voltage [4] and heat [5] based on the fluctuation-dissipation theory. The numerical simulation of a variety of the transmission phenomena is presented in the ferromagnetic-insulator/nonmagnetic-metal hybrids. [1] "Concepts in Spin-Eelectronics" ed. S. Maekawa (Oxford University Press, 2006). [2] Y. Kajiwara et al.: Nature 464, 262 (2010). [3] K. Uchida et al.: Nature Materials, 9, 894 (2010). [4] J. Ohe et al.: Phys. Rev. B 83, 115118 (2011). [5] H. Adachi et al.: APL 97, 252506 (2010) and Phys. Rev. B 83, 094410 (2011).


17

Invited talks

Monday, 9:00 – 9:30

Spin excitations and spin relaxation in subnanoscale

ferromagnets

A. T. Costa

(1), R. B. Muniz

(1), , S. Lounis,

(2) and D. L. Mills

(2)

1) Instituto di Fisica, Universidade Federal Fluminense, 24210-340 Niteroi,

Brazil; (2)

Department of Physics and Astronomy, University of California, Irvine, California 92697, U. S. A.

We shall review our theoretical studies of spin excitations and spin relaxation

(line widths) in ultrathin ferromagnets, along with single spins and dimers on metal surfaces. Also we shall present experimental data that can be compared quantitatively with theory. We find for spin waves of finite wave vector and also for atomic scale spin structures the lifetime of spin excitations is very short by virtue of decay to Stoner excitations in the substrate. Experimental evidence that shows the large linewidths predicted by theory is now in hand. Our fully microscopic studies demonstrate that this is the same mechanism responsible for the spin pumping contribution to the FMR line width in ultrathin ferromagnets on metals. We shall discuss the influence of spin orbt coupling on both spin excitations and relaxation rates; for example in ferromagnetic monolayers on substrates, the Dzyaloshinskii Moriya interaction is activated, with the consequence there is a term linear in wave vector in the dispersion relation of spin waves. Our theory accounts nicely for left/right asymmetries seen in SPEELS studies of both the linewidth and oscillator

strength of spin waves observed in the Fe bilayer on W(110). Finally we shall discuss our theoretical methodology. While many of our studies are based on use of empirical tight binding theory, recently we have developed a mnethod that enables ab initio KKR calculations of the electronic structure to be integrated into our scheme in a manner fully compatible with the Goldstone theorem. We remark, as both theory and experiment demonstrate, the Heisenberg model of localized, exchange coupled spins fails qualitatively for the class of systems we explore. Monday, 9:30 – 10:00

Identification and selection rules of the spin-wave eigen-

modes in a normally magnetized nano-pillar

Grégoire de Loubens, Vladimir Naletov, and Olivier Klein

Service de Physique de l'État Condensé, CEA Saclay, France.

Using magnetic resonance force spectroscopy [1-3] and simultaneously measuring the dc electrical voltage, we demonstrate that the spectra of spin-wave modes excited in a perpendicularly magnetized Py|Cu|Py circular nano-pillar by microwave magnetic field and microwave current are distinctly different. While the spatially uniform microwave magnetic field excites only the axially symmetric modes having azimuthal index l=0, the microwave current, creating a circular microwave Oersted field, excites only the modes having azimuthal index l=1. When the axial symmetry is broken by tilting the bias magnetic field, the modes with l=0 and l=1 can be excited simultaneously by both types of excitation. Moreover, adding a direct current through the nano-

pillar enables to determine which layer contributes mostly to the observed spin-wave modes, because it produces opposite spin transfer torques on each magnetic layer. Experimental results are compared to the theoretical nano-pillar spin-wave mode spectra calculated both analytically and numerically, and the influence of the static and dynamic dipolar coupling between the magnetic layers is analyzed. The proposed identification of the spin-wave modes can be used for the experimental determination of the auto-oscillating mode excited by spin transfer. This work is supported by EU contract NMP-FP7 212257 MASTER.

2nd


18

[1] G. de Loubens, et al., Phys. Rev. Lett. 98, 127601 (2007).

[2] O. Klein, et al., Phys. Rev. B 78, 144410 (2008).

[3] G. de Loubens, et al., Phys. Rev. Lett. 102, 177602 (2009).

Monday, 10:00 – 10:30

Bottom up magnonics: dipolar interaction of a pair of

nanoscale magnetic disks

Paul S. Keatley

1, Prim Gangmei

1, Robert J. Hicken

1, Julie Grollier

2, and

Christian Ulysse3

1School of Physics, University of Exeter, Stocker Road, Exeter EX4 4QL, UK.

2Unité Mixte de Physique CNRS/Thales and Université Paris Sud 11, RD 128,

91767 Palaiseau, France. 3Laboratoire de Photonique et de Nanostructures, Route de Nozay 91460

Marcoussis, France.

Manipulation of the spin wave band structure of a magnonic crystal depends upon the control of dipolar interactions between its constituent magnetic elements. So far most dynamical studies have been performed on large arrays of nano-elements where inter-element dipolar interactions lead to collective excitations, while structural variations at the nanoscale lead to inhomogeneous broadening. It is well known that the spin wave spectrum of a

nano-element can be complicated by the non-uniform profile of the internal field. Typically the nano-element supports a series of confined modes from which a quasi-uniform center mode and localized edge modes have the lowest frequencies. Edge modes may exhibit strong inter-element dipolar interactions but are highly sensitive to the shape of the element and to structural and magnetic edge roughness. The center mode is largely unaffected by such imperfections but gives rise to weaker inter-element dipolar interactions. The large number of normal modes and the presence of inhomogeneous broadening make the dynamics of an array difficult to understand and control. We present an investigation of the dipolar interactions between pairs of Ni81Fe19(15 nm) disks with nominal diameter of 300 nm and nominal separation/diameter (s/d) ratios of 2, 1, 0.6, and 0.3. A pair of interacting

elements is the fundamental sub-unit from which a magnonic crystal may be constructed, and until now it has not been explored by experiment. We have used time-resolved scanning Kerr microscopy, with spatial resolution ~ 500 nm and minimal drift, to perform phase resolved Ferromagnetic Resonance measurements in which the response of each disk is measured separately. We show that the resonance field of nominally identical disks can vary for different separations leading to a significant phase shift between the dynamic response of each disk with respect to the uniform excitation field. We confirm that the variations in the resonance field are larger for the edge

Comparative spectroscopic study performed by MRFM. The upper and lower panels show the spin-wave mode spectra excited by a uniform microwave field

and by a microwave current flowing through the nano-pillar, respectively.


19

mode than for the center mode. Finally, we present evidence that the

variation of the edge mode resonance field can be reduced if the edge-to-edge separation is reduced to less than one radius. We explain this observation in terms of the dynamic dipolar field generated by the edge mode of one disk acting on the edge mode of the other. Optimization and control of this mechanism is essential if phase coherence of edge modes is to be achieved within large arrays of nanomagnets and utilized in magnonic applications. Monday, 11:00 – 11:30

Nonlinear magnonic crystal based on a planar array of

magnetic dots

Gennadii Melkov

1, Yuri Koblyanskiy

1, Valentyn Novosad

2, Konstantin

Guslienko3, Andrei Slavin

4, Andrii Chumak

5, and Burkard Hillebrands

5

1Department of Radiophysics, National Taras Shevchenko University of Kiev,

Kiev 01033, Ukraine. 2Materials Science Division, Argonne National

Laboratory, Argonne, IL, United States. 3Física de Materiales, Universidad del

Pais Vasco, San Sebastian, Spain. 4Department of Physics, Oakland

University, Rochester, Michigan 48309, USA. 5Fachbereich Physik and

Forschungszentrum OPTIMAS, Technische Universität Kaiserslautern, 67663 Kaiserslautern, Germany.

When magnetic elements are reduced to a sub-micrometer size the spin wave spectra of these elements are substantially modified. For example, all the long-wavelength spin wave excitations having the wave number k < 1/R , except the lowest quasi-uniform precession mode (k ~0), are excluded from

the spectrum of a flat circular magnetic dot of a radius R. Moreover, at a certain critical dot radius Rc (which for Permalloy (Py) dots is equal to Rc ~ 100 nm) due to the influence of the exchange interaction, frequencies of all the spin wave excitations in the dot will be above the frequency of the quasi-uniform precession mode, i.e. the frequency degeneracy of the quasi-uniform precession and propagating spin waves will be completely removed. This spectral modification, taking place in sufficiently small magnetic dots, qualitatively changes all the nonlinear dynamic properties of individual dots and planar dot arrays. In particular, the quasi-uniform precession mode in a sufficiently small magnetic dot will not be susceptible to the second-order (four-wave) nonlinear processes that limit the precession amplitude, and, consequently, limit the efficiency of all the other nonlinear processes involving quasiuniform precession, such as parametric amplification, frequency

doubling, Brillouin light scattering, etc. . The theoretical estimations demonstrate that noticeable changes in the nonlinear properties of a magnetic dot will appear starting from the dot radius of R = 1000 nm, because in such a dot spin waves having the wave number k ~ 10

4 cm

-1 and most effectively

interacting with the quasi-uniform precession mode would be excluded from the dot spectrum. In planar arrays of closely packed dots additional spectral transformations caused by the interdot dipole-dipole interaction will take place. Thus, the nonlinear dynamic properties of magnonic crystals formed by planar arrays of magnetic dots will be determined by the dot radius and the interdot spacing. To check these ideas we compared experimentally the nonlinear process of a sub-harmonic generation by parametric microwave pumping in a continuous Permalloy film of the thickness L = 100 nm and in a planar array of non-interacting magnetic dots (radius R = 1000 nm, thickness L = 100 nm,

separation between the dot centers l = 2000 nm). In both magnetic media the generation of the sub-harmonic signal was caused by the application of a spatially uniform parallel (to the direction of the in-plane bias field H) microwave pumping of the frequency fp = 9.4 GHz. The bias magnetic field H

was chosen to satisfy the conditions of the ferromagnetic resonance at the sub-harmonic of the pumping signal fp/2 = f0(H), where f0 is the frequency of the quasi-uniform precession.

2nd


20

This work was supported by the "Material World Network" grant jointly funded by the USA, Ukraine, Germany, and Spain, and by the Deutsche Forschungsgemeinschaft. Monday, 11:30 – 12:00

Spin-wave excitations in magnonic crystals

Yuri Filimonov

1, Yuri Khivintsev

1,3, Sergei Nikitov

2,3, Evgenii Pavlov

2, Valentin

Sakharov2, and Sergei Vysotskii

1

1Kotel’nikov Institute of Radio Engineering and Electronics of RAS, Saratov

Branch; 2Kotel’nikov Institute of Radio Engineering and Electronics of RAS,

Moscow; 3Saratov State University, Saratov, Russia.

The properties of spin-wave excitation in periodic magnetic structures

(magnonic crystals (MC)) were investigated by FMR and VNA techniques. The 1D and 2D MC based on yttrium iron garnet (YIG) and ferromagnetic (Py, Co) films with micron size patterns and period Λ were fabricated and their parameters were tested using vibrating sample magnetometer, atomic and magnetic force microscopy, and four-probe magnetoresistance (for ferromagnetic films). For MCs based on YIG films both propagating and localized excitations were studied. For propagating magnetostatic waves both collinear and noncollinear Bragg diffraction were investigated. In case of 1D MC spin-wave spectra quantization induced by surface microstructure was observed. An influence of the parametric instability processes on magnetostatic surface waves (MSSW) Bragg resonances was studied. It was shown that parametric process can suppress the Bragg resonances. Bragg resonances of MSSW in metallized 1D MC were investigated as a

function of dielectric spacer thickness t. It was shown that for t<Λ/π Bragg resonance disappear. Three types of magnonic crystals based on ferromagnetic films were studied: magnetic antidot lattices, continuous magnetic films deposited on patterned substrates and structures with in-plane combination of permalloy (Py) and cobalt (Co) films like periodically alternating Co and permalloy Py microstripes. For tangentially magnetized Py antidot square lattice we found spin-wave modes hybridization effects while varying angle between MC axis and bias field. In continuous Py films sputtered on meander-like patterned substrates we found lateral spin-wave spectra quantization. For Py film sputtered on Si patterned substrate anisotropic magnetoresistance effect ~2% was also found. For MC with periodically alternating Co an Py stripes MSSW resonances across the stripes width as well as uniform modes in Co and Py

stripes were observed. This work was supported by RFBR (grants # 09-07-00186 and 11-07-00233), Federal Grant-in-Aid Program «Human Capital for Science and Education in Innovative Russia» (governmental contract # П485, 02.740.11.0014 and 14.740.11.0077), Federal Agency of Education of the Russian Federation (project # 2.1.1/2695) and the Grant from Government of Russian Federation for Support of Scientific Research in the Russian Universities Under the Guidance of Leading Scientists (project No. 11.G34.31.0030). Monday, 14:00 – 14:30

Magnon gases and condensates

Alexander Serga1, Vasil Tiberkevich

2, Christian Sandweg

1, Vitaliy Vasyuchka

1,

Andrii Chumak1, Björn Obry

1, Gennadii Melkov

3, Andrei Slavin

2, and Burkard

Hillebrands1

1Fachbereich Physik and Forschungszentrum OPTIMAS, University of

Kaiserslautern, 67663 Kaiserslautern, Germany. 2Department of Physics,

Oakland University, Rochester, Michigan 48309, USA. 3Department of

Radiophysics, National Taras Shevchenko University of Kiev, Kiev 01033, Ukraine.


21

The behavior of a magnon gas in a magnetic insulator which is driven by

pulsed microwave parametric pumping will be presented. The dynamics of a parametrically created magnon condensate (at half of the pumping frequency), of a gaseous magnon phase, and of the Bose-Einstein condensate (BEC) formed at the lowest energy state of the magnon gas were observed using time-resolved Brillouin light scattering (BLS) spectroscopy. Special attention was focused on the pump-free evolution of the magnetic medium after pumping. The work revealed detailed aspects of the elegant and powerful fundamental analogy between magnon condensates and ultracold quantum gases. It was previously shown [1] that, in order to obtain a magnon BEC, a low temperature is not required because a high density of quasi-particles can be readily achieved by external pumping. In our experiment we created the quasi-equilibrium BEC by applying a long pumping pulse and observed the evolution

of the condensate in the presence and absence of the pumping source. After the pumping was switched off, the intensity of the directly injected magnons was found to decay exponentially in about 45 ns. The gaseous magnon phase which lays between the region of parametrically excited magnons and the bottom of the magnon spectrum also decays exponentially after the pumping pulse ends. Nevertheless, the BEC at the bottom of the spectrum has a different, unexpected behavior when the pumping is switched off. A dramatic jump in the density of the condensed magnons is observable. The rise time of the BEC is perfectly correlated with the decay time of the primary injected magnons. Afterwards, the density of the magnon condensate decays in about 700 ns, which is the intrinsic decay time of YIG. This behavior is relatively easily explained once one realizes that the thermalization of the pumped magnon gas occurs only within a narrow energy region near the bottom of the spectrum, where the magnon gas is strongly overheated by pumping

(estimated temperature is more than 30000 K). As a result of nonlinear magnon-magnon scattering, a magnon may gain additional energy and leave the thermalized region, thus reducing the average energy of the remaining magnons. This mechanism is similar to the well-known process of evaporative cooling in real atomic gases, but is much more pronounced due to its low value of “cutoff” energy. A simple analytical model of such “evaporative supercooling” of a quasi-equilibrium magnon gas gives a good quantitative account of the experimentally observed phenomena. Financial support by the DFG (SFB/TRR 49) is gratefully acknowledged. [1] S.O. Demokritov, V.E. Demidov, O. Dzyapko, G.A. Melkov, A.A. Serga, B. Hillebrands, and A.N. Slavin, Bose-Einstein condensation of quasi-equilibrium

magnons at room temperature under pumping, Nature 443, 430 (2006).

Monday, 14:30 – 15:00

Manipulation of spin waves in yttrium iron garnet thin films

through Interfacial spin scattering

Mingzhong Wu,

1 Zihui Wang,

1 Yiyan Sun,

1 Vasil Tiberkevich,

2 and Andrei

Slavin2

1 Department of Physics, Colorado State University, Fort Collins, CO 80523,

USA.2 Department of Physics, Oakland University, Rochester, MI 48309, USA

Spin waves in magnetic films have many properties that can be utilized for microwave signal processing [1-3] and logic operations [4-6]. These applications, however, are bottlenecked by the damping of spin waves. One way to compensate the spin-wave damping is to use parametric pumping

[7,8]. This method, however, requires the use of an external microwave signal with a frequency twice that of the spin wave and a delicate resonator for the delivery of this signal to the film. This presentation reports on a new method for the amplification of spin waves. Specifically, the presentation reports the first demonstration of the electric manipulation of spin waves in yttrium iron garnet (YIG) thin films via interfacial spin scattering (ISS). Experiments used

a 4.6 m-thick YIG film strip with a 20 nm-thick Pt capping layer. A dc pulse was applied to the Pt film that produced a spin current along the Pt thickness direction via the spin-Hall effect. As the spin current scatters off the surface of

2nd


22

the YIG film, it exerts a torque on the YIG surface spins. Due to the dipolar and exchange interactions, the effect of this torque is extended to other spins across the YIG thickness and thereby to spin-wave pulses traveling in the YIG film. The net effect of the ISS process depends critically on the relative orientation of (1) the magnetic moments of the electrons in the Pt layer that scatter off the YIG surface and (2) the precession axis of the magnetic moments on the YIG surface. When they are anti-parallel, the spin-wave damping is reduced and the amplitude of a traveling spin-wave pulse is increased. In a parallel configuration, the pulse experiences an enhanced attenuation. The ISS process can also raise or reduce the power level to which high-power spin-wave pulses saturate due to nonlinear damping. Since the parallel/anti-parallel configuration can be changed simply by reversing the direction of the dc current, our results demonstrate a rather simple new approach for the control of spin waves.

[1] P. Kabos and V. S. Stalmachov, Magnetostaic Waves and heir

Applicaations (Chapman and Hall, London, 1994). [2] D. D. Stancil and A. Prabhakar, Spin Waves: Theory and Applications

(Springer, New York, 2009). [3] J. D. Adam et al., IEEE Trans. Microwave Theory Tech. 50, 721 (2002).

[4] S. Bance et al., J. Appl. Phys. 103, 07E735 (2008).

[5] T. Schneider et al., Appl. Phys. Lett. 92, 022505 (2008).

[6] Khitun et al., J. Phys. D: Appl. Phys. 43, 264005 (2010).

[7] P. A. Kolodin et al., Phys. Rev. Lett. 80, 1976 (1998).

[8] V. Bagada et al., Phys. Rev. Lett. 79, 2137 (1997).

Monday, 15:00 – 15:30

Magnon and phonon excitation at the Fe(100)/O surface by

scattering of spin-polarized electrons

Juergen Kirschner*

Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle,

Germany

We study the magnon and phonon spectra of a Fe(100) surface covered by one monolayer of oxygen atoms. The oxygen atoms acquire a sizeable magnetic moment oriented parallel to the Fe moments, and parallel to the surface. The spectrum of inelastically scattered electrons shows a variety of energy losses and energy gains, dispersing with the momentum transfer parallel to the surface. In general, both magnons and phonons show a spin dependent excitation cross section and both elementary excitations coexist on

the surface. They can be distinguished experimentally by their different response with respect to the primary electron spin: magnons are excited only by minority electrons, because of the conservation of the total angular momentum, while phonons are excited essentially by the electron charge, independent of spin. We mapped out the dispersion for magnons and phonons and compared to theoretical first principles calculations for surface and bulk phonons. Good agreement was found. * In collaboration with Kh. Zakeri, Y. Zhang, J. Prokop, T. R. F. Peixoto, W. X. Tang, P. A. Ignatiev, V. S. Stepanyuk Monday, 16:00 – 16:30

The role of angular momentum in ultrafast magnetization

dynamics

Andrei Kirilyuk

Radboud University Nijmegen, Institute for Molecules and Materials,

Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands

Many peculiarities of the magnetization dynamics are related to the fact that a certain amount of angular momentum is associated with magnetic moment.


23

Particularly strong manifestation of this can be observed in multisublattice

magnets. Here, the dynamics of angular momentum is studied in ferrimagnetic rare-earth – transition metal alloys, such as GdFeCo, where both magnetization and angular momenta are temperature dependent. Depending on their composition, these ferrimagnets can exhibit a magnetization compensation temperature TM where the magnetizations of the sublattices cancel each other and similarly, an angular momentum compensation temperature TA where the net angular momentum vanishes. At the latter point, the frequency of the homogeneous spin precession diverges. As a consequence, ultrafast heating of a ferrimagnet across its compensation points may result in a subpicosecond magnetization reversal [1]. Moreover, we have experimentally demonstrated that the magnetization can be manipulated and even reversed by a single 40 femtosecond circularly polarized laser pulse, without any applied magnetic field [2-4]. This optically

induced ultrafast magnetization reversal is the combined result of laser heating of the magnetic system with strong magneto-optical effects. The direction of this opto-magnetic switching is determined only by the helicity, i.e. angular momentum, of light. However, the latest results show that even unpolarized, or linearly polarized pump pulse may result in the magnetization reversal, which happens solely due to a balance of the angular momentum of the two sublattices [5]. This novel reversal pathway is shown to occur via a strongly non-equilibrium state with two sublattices in ferro-magnetic alignment.

[1] C.D. Stanciu et al., Phys. Rev. B 73, 220402 (2006); Phys. Rev. Lett. 99,

217204 (2007). [2] C. D. Stanciu et al, Phys. Rev. Lett. 99, 047601 (2007).

[3] A. Kirilyuk, A.V. Kimel, and Th. Rasing, Rev. Mod. Phys. 82, 2731 (2010).

[4] K. Vahaplar et al., Phys. Rev. Lett. 103, 117201 (2009).

[5] I. Radu et al., Nature 472, 205 (2011).

Monday, 16:30 – 17:00

Dynamics of spin vortices: from physics to cancer therapy

V. Novosad,

1 D.-H. Kim,

1 E. A. Rozhkova,

2 I. Ulasov,

3 M. S. Lesniak,

3

T. Rajh,2 and S. D. Bader,

1,2

1Materials Science Division, Argonne National Laboratory, Argonne, IL, USA. 2Center for

Nanoscale Materials, National Laboratory, Argonne, IL, USA. 3The University of Chicago

Pritzker School of Medicine, Chicago, USA.

The magnetic ground state of magnetically soft thin film ferromagnets in

confined geometries (on the micrometer scale) consists of a curling spin configuration, known as a magnetic vortex state. The vortex is characterized by an in-plane continuous swirling closure spin structure with a small (~10 nm) core region where the spins tilt out of the plane. Previous experiments examining the intrinsic spin dynamics of the vortex core under the influence of pulsed fields have detected a translational or gyrotropic eigenmode consisting of sub-GHz frequency spiral-like motion of the vortex core about its equilibrium position. The sense of the core rotation is uncorrelated with the vortex chirality and that it is determined solely by the core polarization. It was also shown that the magnetic vortex core can be reversed using rf magnetic fields of very small amplitude], whereas up to several kOe field is required to switch the core with static field. The other higher frequency (5-10 GHz) excitations can be understood (within some approximation) as the usual spin waves in restricted geometries. Furthermore, when the vortex microdisks suspended in

aqueous solution demonstrate rotational motion response when subjected to an AC magnetic field [1]. Such dynamic response can be employed to advance novel therapies such as “on demand” drug delivery [2] or magneto-mechanical cancer cell destruction [3]. To demonstrate the latter, the gold-coated lithographically defined microdisks with an Fe-Ni magnetic core were biofunctionalized with anti-human-IL13a2R antibody for specifically targeting human glioblastoma cells. When an alternating magnetic field is applied the vortices shift, leading to the microdisks oscillation that causes a mechanical force to be transmitted to the cell. Cytotoxicity assays, along with optical and

2nd


24

atomic force microscopy studies, show that the spin vortex-mediated stimulus creates two dramatic effects: (a) membrane disturbance and compromise, and (b) cellular signal transduction and amplification, leading to robust DNA fragmentation and, finally, programmed cell death. The experiments reveals that by employing biofunctionalized magnetic vortex microdisks the magnetic fields of low frequency of a few tens of Hz and of small amplitude of < 100 Oe applied during only 10 minutes was sufficient to achieve ~90% cancer cells destruction in vitro. [1] E. A. Rozhkova, et al., J. Appl. Phys. 105, (2009) 07B306.

[2] D.-H. Kim, et al., J. Mat. Chem. (2011), DOI: 10.1039/c1jm10272a. [3] D.-H. Kim, et al., Nature Materials, 9, 165 - 171 (2010).

This work and the use of the Center for Nanoscale Materials at Argonne

National Laboratory were supported by UChicago Argonne, LLC, Operator of Argonne National Laboratory (``Argonne''). Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under Contract No. DE-AC02-06CH11357. Work at the University of Chicago is supported by the National Cancer Institute (R01-CA122930), the National Institute of Neurological Disorders and Stroke (K08-NS046430), the Alliance for Cancer Gene Therapy Young Investigator Award and the American Cancer Society (RSG-07-276-01-MGO). Monday, 17:00 – 17:30

Photo-magnonics

Benjamin Lenk, Fabian Garbs, Henning Ulrichs*, and Markus Münzenberg

Physikalisches Institut, Georg-August-Universität Göttingen, Germany,

*current address: Institut für Angewandte Physik, Westfälische Wilhelms-University at Münster, Germany.

All-optical femtosecond laser experiments over the last years, it became valuable novel method to study spin-waves and their relaxation paths. Laser pulses with a duration of 30-60 fs from a Ti:Sa regenerative laser system are used for all-optical excitation. First, I want to enlighten the intrinsic spin-flip processes involved [1]: local single spin-flip excitations decay into exchange spin waves and dipolar surface modes of lower energy with well defined k-vector. They can be controllably excited. The laser excitation allows creating well defined modes with a specific k-value all-optically in the plain films. The optical excitation and detection allows a very versatile access to spin

dynamics.

Magnonic crystal structures based on anti-dots, a two dimensional periodic modification here with distances in the spin-wave length range of dipolar spin waves, allow the control of the spin-wave modes [2]. The periodic modification defines the spin-wave bands and their energy. Two regions can be distinguished in our experiments: different to photonics, the modes depend strongly on the strength of the magneto-static potential at around each hole site – the dipolar field. This leads to a mode localization. However for filling fractions lower than 10% also Bloch states are found in low damping

ferromagnetic metals with a propagation length of >100 m of squared, hexagonal or honeycomb symmetry [3]. Bloch states at the zone boundary dominate the magnetization dynamics. One example for a distinct modification of the magnonic periodic structure is a line defect that can function as a wave guide for spin-wave frequencies inside the magnonic gap region, to be further

functionalized in the future. [1] M. Münzenberg, Ferromagnets stirred up, Nature Mater. 9, 184 (2010). Thermal mechanisms in laser-induced femtosecond spin dynamics, U. Atxitia, O. Chubykalo-Fesenko, J. Walowski, A. Mann, and M. Münzenberg, Phys. Rev. B 81, 174401 (2010). [2] The building blocks of magnonics (review), B. Lenk, H. Ulrichs, F. Garbs, M. Münzenberg, to appear in Physics Reports, arXiv:1101.0479.

http://www.nature.com/nmat/journal/v9/n3/full/nmat2706.html

http://prb.aps.org/abstract/PRB/v81/i17/e174401


http://arxiv.org/abs/1101.0479


25

[3] Magnonic spin-wave modes in CoFeB antidot lattices H. Ulrichs, B. Lenk,

and M. Münzenberg, Appl. Phys. Lett. 97, 092506 (2010). Website: http://www.uni-goettingen.de/de/124076.html Tuesday, 9:00 – 9:30

Spin wave propagation in magnonic crystals made from

nanopatterned permalloy

Dirk Grundler

Lehrstuhl fuer Physik funktionaler Schichtsysteme, Technische Universitaet Muenchen, Physik Department, James-Franck-Str. 1, D-85747 Garching,

Germany.

Collective spin excitations in nanopatterned ferromagnets have regained great interest recently [1]. In particular magnonic crystals, i.e. the magnetic counterpart of photonic crystals, are expected to open intriguing perspectives for the controlled transmission and manipulation of spin waves. Formed by a periodically patterned ferromagnet they offer an artificially tailored band structure for magnons with allowed minibands and forbidden frequency gaps. Also meta-materials properties might follow [2]. We have prepared permalloy thin film devices being, both, periodically patterned in one (1D) and two (2D) dimensions [3-6]. Exploring a 1D magnonic crystal prepared from collinear nanowires we have found that the band structure can be reprogrammed via different magnetic states [3]. We have also performed all-electrical spin-wave spectroscopy on antidot lattices, i.e., 2D arrays of periodic holes [4, 5]. Here magnonic crystal behavior and meta-materials properties were found with surprisingly fast spin-wave propagation velocities [6]. We report our recent

results obtained on magnonic crystals. We gratefully acknowledge collaborations and discussions with C.H. Back, H. Bauer, F. Brandl, G. Dürr, G. Gubbiotti, D. Heitmann, R. Huber, M. Kostylev, M. Krawczyk, V. Kruglyak, M. Madami, S. Neusser, J. Podbielski, D. Schmidt-Landsiedel, T. Schwarze, M.L. Sokolovsky, S. Tacchi, J. Topp, and G. Woltersdorf. The research leading to these results has received funding from the European Community‟s Seventh Framework Programme (FP7/2007-2013) under Grant Agreement no. 228673 and the German Excellence Cluster ‟Nanosystems Initiative Munich‟. [1] S. Neusser and D. Grundler: “Magnonics: Spin waves on the nanoscale”, Adv. Mater. 21, 2927 (2009); V.V. Kruglyak, S.O. Demokritov, and D. Grundler: “Magnonics”, J. Phys. D: Applied Physics 43, 264001 (2010); and

references therein. [2] S. Neusser, “Spin Waves in Antidot Lattices: From Quantization to Magnonic Crystals”, Ph D Thesis, Technische Universitaet Muenchen, submitted. [3] J. Topp, D. Heitmann, M.P. Kostylev, and D. Grundler: “Making a reconfigurable artificial crystal by ordering bistable magnetic nanowires”, Phys. Rev. Lett. 104, 207205 (2010). [4] S. Neusser, B. Botters, M. Becherer, D. Schmitt-Landsiedel, and D. Grundler: “Spin wave localization between nearest and next-nearest neighboring holes in an antidot lattice”, Appl. Phys. Lett. 93, 122501 (2008). [5] S. Neusser, G. Duerr, H. G. Bauer, S. Tacchi, M. Madami, G. Woltersdorf, G. Gubbiotti, C. H. Back, and D. Grundler: "Anisotropic propagation and damping of spin waves in a nanopatterned antidot lattice", Phys. Rev. Lett. 105, 067208 (2010).

[6] S. Neusser, G. Duerr, S. Tacchi, M.L. Sokolovsky, M. Madami, G. Gubbiotti, M. Krawczyk, and D. Grundler: "Magnonic minibands in antidot lattices with large spin-wave propagation velocities", submitted.

http://apl.aip.org/resource/1/applab/v97/i9/p092506_s1

http://www.uni-goettingen.de/de/124076.html

2nd


26

Tuesday, 9:30 – 10:00

Controlling spin wave propagation in planar magnonic crystal

Gianluca Gubbiotti,

1,2 Silvia Tacchi,

1 Marco Madami,

1 and Giovanni Carlotti

1

1CNISM-Unità di Perugia, Dipartimento di Fisica, Via A. Pascoli, I-06123,

Perugia, Italy. 2 Istituto Officina dei Materiali (CNR-IOM), Sede di Perugia, c/o Dipartimento

di Fisica, Via A. Pascoli, I-06123 Perugia,Italy.

Magnonic Crystals (MCs) represents a new class of materials with periodically modulated magnetic properties were allowed bands and ranges of forbidden gaps can be recognized in the dispersion curves of spin excitations. Up to now, experiments have been concentrated on one-dimensional (1D) MCs

consisting of arrays of longitudinally magnetized nanostripes, with the wave vector directed along the array periodicity.[1,2] These studies demonstrated the existence of dispersive Bloch waves propagating through the array. On the contrary, there are only a few reports on either the imaging [3] or the magnetic band structure [4] of collective excitations in two-dimensional (2D) MCs. In particular a complete mapping of the Brillouin zone (BZ) and a detailed discussion of the physics underpinning the dispersion curves of magnonic modes is still lacking in the literature. In this work, the band diagram of 2D MCs constituted either by ordered arrays of micrometric magnetic elements, interacting via the dynamical dipolar field, or antidot arrays, i.e. a periodic array of holes in a continuous magnetic film, are experimentally investigated by Brillouin light scattering technique. In the latter case, we also consider the spin wave properties in binary component arrays, where ferromagnetic dots are embedded into a thin film of different ferromagnetic material. These

studies are preliminary to the design of future microwave devices based on useful functionality of magnonic crystals, such as their frequency and wavevector selectivity (which directly results from their periodicity and the associated band spectrum), as well as their controllability by external magnetic fields and magnetic contrast between two different ferromagnetic materials. [1] G. Gubbiotti, S. Tacchi, G. Carlotti , N. Singh , S. Goolaup , A.O. Adeyeye, and M. Kostylev, Appl. Phys. Lett. 90, 092503 (2007).

[2] Z. K. Wang, V. L. Zhang, H. S. Lim, S. C. Ng, M. H. Kuok, S. Jain, and A. O. Adeyeye, Appl. Phys. Lett. 94, 083112 (2009).

[3] V.V. Kruglyak, P.S. Keatly, A. Neudert, R.J. Hicken, J.R. Childress, and J.A. Katine, Phys. Rev. Lett. 104, 027201 (2010).

[4] S. Tacchi, M. Madami, G. Gubbiotti, G. Carlotti, H. Tanigawa,T. Ono, and

M.P. Kostylev, Phys Rev. B 82, 024401 (2010).

This work is supported by the European Community's Seventh Framework Programme (FP7/2007-2013) under Grant Agreements n°228673 (MAGNONICS).

Tuesday, 10:00 – 10:30

Magnonics beyond magnonic crystals: magnonic meta-

materials and devices

Volodymyr Kruglyak

1, Yat-Yin Au

1, Mykola Dvornik

1, Rostislav Mikhaylovskiy

1,

Toby Davison1, Ehsan Ahmad

1, Vera Tkachenko

2, and Andrey Kuchko

2

1University of Exeter, United Kingdom.

2Donetsk National University, Ukraine

The recent renaissance of magnonics was a result of the remarkable technological, experimental, and theoretical advances that made it possible not only to study but also to explore ways to exploit spin waves in magnetic nanostructures, with magnonic crystals having played a decisive role in defining the identity of the new research field [1]. On the other hand, a lot of interest has been generated by the prospectus for creation of magnonic meta-materials [2,3] and logic devices [1,4,5].


27

In this talk, we will review our most recent results along the latter research

directions. In particular, we will demonstrate an architecture facilitating excitation of spin waves in multiple places on a magnonic logic chip and will discuss opportunities and limitations arising from exploiting 3D magnetic geometries for design of spin wave resonances in magnonic metamaterials and waveguides. The research leading to these results has received funding from the European Community's Seventh Framework Programme (FP7/2007-2013) under Grant Agreements n°233552 (DYNAMAG) and n°228673 (MAGNONICS) and from the Engineering and Physical Research Council (EPSRC) of the UK. [1] V. V. Kruglyak, S. O. Demokritov, and D. Grundler, J. Phys. D – Appl. Phys. 43, 264001 (2010).

[2] V. V. Kruglyak, P. S. Keatley, A. Neudert, R. J. Hicken, J. R. Childress, and J. A. Katine, Phys. Rev. Lett. 104, 027201 (2010).

[3] R. V. Mikhaylovskiy, E. Hendry, and V. V. Kruglyak, Phys. Rev. B 82,

195446 (2010). [4] S. V. Vasiliev, V. V. Kruglyak, M. L. Sokolovskii, and A. N. Kuchko, J. Appl.

Phys. 101, 113919 (2007).

[5] Y. Au, T. Davison, E. Ahmad, P. S. Keatley, R. J. Hicken, and V. V. Kruglyak, Appl. Phys. Lett. 98, 122506 (2011).

Tuesday, 11:00 – 11:30

Spin pumping at ferromagnet (Fe,YIG)/normal metal (Au,Ag)

interfaces and spin transport in Au and Ag films

B. Heinrich

1, B. Kardasz

1, C. Burrowes

1, E. Montoya

1, E. Girt

1, Young-Yeal

Song2, Yiyan Sun

2, and Mingzhong Wu

2

1Physics Department, Simon Fraser University, Burnaby, BC, V5A 1S6,

Canada. 2Physics Department, Colorado State University, Fort Collins, CO

80523, USA.

Spin injection across the metallic ferromagnet (Fe) and magnetic insulator (YIG)/normal metal (Au, Ag) interface was studied using ferromagnetic resonance (FMR) from 10 to 74 GHz. Spin transport in crystalline Au and Ag layers was investigated using single-magnetic-layer Ag,Au/Fe(001) and double-magnetic-layer Fe/Ag,Au/Fe(001) structures prepared by MBE on 2x6 GaAs(001) reconstructed templates. Pure spin currents were injected at the Ag,Au/Fe interface into the Ag and Au layers by using rf spin pumping effects. For the Au,Ag/Fe/GaAs(001) structures, the spin pumping introduces non-local interface Gilbert damping. This contribution

increases with the normal metal (NM) layer thickness and eventually saturates when its thickness is larger than the spin diffusion length in the NM layer. In the Fe/Au,Ag/Fe/GaAs(001) structures, both spin-pumping and spin-sink effects are present. The magnetic damping was investigated by ferromagnetic resonance (FMR) techniques. The data analyses were carried out using Kirchhoff‟s laws of spintronics. The Ag (n (atomic layers) = 20, 100, 300, 500, and 1500) and Au (n=20, 80, 150, 200, 250, 300, and 1500) allowed one to investigate nonlocal spin transport from ballistic responses to spin-diffusion limits. The sheet conductance measurements allowed one to determine the role of electron momentum interface diffuse scattering and estimate an effective momentum relaxation time in the Ag and Au layers. The results of the sheet conductance and FMR and time-resolved MOKE measurements determined the electron momentum and spin flip relaxation times and the corresponding spin diffusion lengths in the Ag and Au layers. The

measurements were carried out from room to cryogenic temperatures. A newly emerging field called spin caloritronics addresses the generation of spin current by thermal gradient. In his pioneering work, Slonczewski [1] has shown that a higher efficiency in spin torque transfer devices can be achieved by using spin transport driven by thermal gradients in magnetic insulator/normal metal structures. It was shown by Xiao et al. [2] that the transfer of spin momentum is governed by the real part of interface spin

mixing conductance g. It is therefore of an utmost importance to determine the strength of the spin mixing conductance at the magnetic insulator/ normal

2nd


28

Fig.1 Rotation of magnon wavepacket

Fig.2 Dispersion of MSFVW in YIG

and corresponding Berry curvature

metal interface. Spin injection across the ferromagnetic insulator (YIG)/normal metal (Au) interface was studied using FMR. The spin mixing conductance

was determined by comparing the Gilbert damping constant in as grown (bare) YIG films with those covered by Au/Fe/Au layers. The YIG films were grown by pulsed laser deposition on a GGG substrate. The Fe layer in Au/Fe/Au acted as a spin sink. In a 9.0nmYIG/2.0nmAu/4.3nmFe/6.1nmAu structure, the FMR lines of YIG were shifted to lower external magnetic fields compared to that in a bare YIG film. This shows that the YIG and Fe films were coupled by ferromagnetic interlayer exchange coupling. The interlayer exchange coupled samples also displayed an increased Gilbert damping

constant compared to that in bare YIG. This provides the direct evidence for spin pumping at the YIG/Au interface. The transfer of spin momentum across the YIG interface is surprisingly efficient with the spin mixing

conductance g.1.21014

cm-2

which is 10% of that at the Fe/Au interface.

[1] J. Slonczewski, Phys.Rev. B 82, 0544-3 (2010)

[2] J. Xiao, G. Bauer, K. Uchida, E. Daitoh, and S. Maekawa, Phys.Rev.B 81,

214418 (2010) Tuesday, 11:30 – 12:00

Theory of rotations of magnon wavepacket and magnon Hall

effect

Ryo Matsumoto

A, and Shuichi Murakami

A,B

Tokyo Institute of Technology

A, PRESTO, JST

B

In electron systems, various kinds of Hall effects are attributed to Berry curvature in momentum space. This Berry curvature involves derivative of the Bloch wavefunction with respect to the wavenumber, and it is determined by the band structure. In a semiclassical picture it gives rise to a velocity perpendicular to the electric field, causing the Hall effect. In my presentation we study dynamics of a magnon wavepacket, in analogy to electrons. Here magnons include both quantum-mechanical magnons by spin

exchange and magnetostatic spin wave in the classical electromagnetic theory. We theoretically find that the magnon wavepacket undergoes two types of rotational motions: self-rotation and edge current of magnon, as schematically shown in Fig.1. Such magnon edge current causes thermal Hall effect of magnon. The magnon thermal Hall conductivity is calculated by two methods: the semiclassial theory based on edge current, and the linear response theory. We obtained the same result from the two methods. Our result

contains new correction terms to the previous works, and these correction terms are attributed to the orbital motions of magnon wavepackets. We discuss two materials Lu2V2O7 and YIG as an example. In YIG, we find that for the MSSW and MSBVW the Berry curvature is zero and there are no wavepacket rotations. For the MSFVW, on the other hand, the Berry curvature is calculated as in Fig. 2, and the wavepacket rotation and Hall effect is predicted theoretically. Such rotational motions are expected to be observable experimentally.


29

[1] R. Matsumoto, S. Murakami, arXiv:1103.1221, to appear in Phys. Rev. Lett. Wednesday, 9:00 – 9:30

Microwave phenomena in planar ferrite-ferroelectric

heterostructures: theory and applications

Natalia Grigoryeva, Boris Kalinikos, Alexander Kondrashov, Andrey Nikitin,

and Alexey Ustinov Saint Petersburg Electrotechical University, 197376, Saint Petersburg, Russia

One of the modern areas in physics and technology comprises fundamental

investigations and engineering applications of multiferroic materials. Multiferroic materials can be divided into several classes. One of the classes consists of the so-called “natural multiferroics” (see, e.g. [1]). Another class consists of the “artificial multiferroics” that are fabricated by a combination of different type of materials, such as ferrite and ferroelectric films (see, e.g. [2]), and field-induced periodical variations of the magnetic and/or electric parameters of these materials. It is clear that the combination of ferrite and ferroelectric films in a multi-layered structure provides the possibility of simultaneous “magnetic” and “electric” tuning of its microwave properties. From our point of view, the artificial multiferroics in a form of multi-layered structures, such as yttrium iron garnet (YIG) and barium strontium titanate (BST) layered heterostructures, demonstrate effects that are currently the most interesting for microwave applications. Such effects include electrically tunable linear and nonlinear phase shifts, electrically tunable group time delay,

electrically tunable frequency filtering, electronically controllable formation of stable spin-wave envelope solitons, and chaotical generation of microwave waveforms. These phenomena have already led or may lead in the future to the elaboration of new devices for microwave signal processing. Particularly, the recent advances in the area contain the use of nonlinear effects in hybrid ferrite-ferroelectric layered materials to elaborate nonlinear microwave devices. The aim of this presentation is two-fold: (1) to review briefly the theory and physics of linear and nonlinear hybrid “electromagnetic wave”–“spin wave” processes in thin ferrite-ferroelectric layered structures as a basis for device applications, and (2) to present two types of device structures, namely, a feedback active ring and nonlinear phase shifter. The main attention will be given to the active ring based on YIG/BST heterostructure. Active ring-based devices will be presented, including the single-mode and

multi-mode frequency tunable resonators, tunable Q-factor resonator, as well as stable and chaotic solitonic waveform generators.

[1] D. Khomskii, “Classifying multiferroics: Mechanisms and effects”, Physics 2, 20 (2009).

[2] Ce-Wen Nan, et al., “Multiferroic magnetoelectric composites: Historical perspective, status, and future directions”, J. Appl. Phys. 103, 031101 (2008).

Wednesday, 9:30 – 10:00

Magnetic materials for on-wafer microwave devices

Z. Celinski, I. Harward, Y. Nie, B. Kuanr, Y.V. Khivintsev, V.V. Zagorodnii, and

R.E. Camley

Center for Magnetism and Magnetic Nanostructures, University of Colorado at Colorado Springs (UCCS),

1420 Austin Bluffs Parkway, Colorado Springs, CO, 80918, USA.

We describe experimental efforts in which the main objective is to develop a series of on-wafer tunable microwave devices based on the nonreciprocal or nonlinear properties of magnetic materials. Specifically, we studied two classes of devices: (1) isolators, which use the nonreciprocal features of waves interacting with magnetic materials in confined structures and (2) devices such

2nd


30

as a signal-to-noise enhancer (SNE), which use nonlinear effects in ferromagnetic metals. Moreover, the development processes for these devices must include materials which are compatible with the processes used for high frequency electronics, thus allowing on-wafer integration. Among microwave materials, hexagonal ferrites are very important for high frequency applications. Recently, we have successfully deposited M-type barium hexagonal ferrite films, with the crystallographic c axis out of plane, onto a Pt template using a Metallo-Organic Decomposition technique. For the best films, the XRD patterns revealed strong (00l) reflections and a texture fraction of 0.953, confirming the out of plane c axis orientation. Static (magnetometry) and dynamic (Ferromagnetic Resonance) measurements revealed a high effective out of plane anisotropy field, high perpendicular remanent magnetization (Mr = 0.93Ms), and narrow FMR linewidth. For the on-wafer isolators we used electroplated magnetic nanowires as the active

element. These nanowires were characterized using FMR. We will discuss the high frequency properties of these materials and their application in microwave devices Our approach can reduce the weight and increase the reliability of microwave devices. We expect that the use of nonlinear or nonreciprocal properties of ferromagnetic materials in on-wafer microwave devices will likely open new directions for highly advanced communication systems. Wednesday, 10:00 – 10:30

Microwave magnetoelectric interactions in multiferroic

structures and novel devices

Yuri Fetisov

Moscow State Institute of Radio Engineering, Electronics and Automation,

119454 Moscow, pr. Vernadskogo 78, Russia.

The paper describes new phenomena recently observed at interaction of microwaves (1-100 GHz) with multiferroic structures possessing simultaneously ferromagnetic and ferroelectric ordering. Parameters of such artificially fabricated structures consisting of alternate ferromagnetic and ferroelectric layers can be changed by applying external magnetic H and electrical E fields. Variation of the structures parameters is due to magnetoelectric (ME) interaction which is realized through combination of piezoelectricity and magnetostriction via mechanical coupling between the layers or through the electrical field induced change in the dielectric permeability of the ferroelectric layer. This property allows control of magnetic

characteristics, frequency of the ferromagnetic resonance (FMR), and characteristics of propagating spin waves (SW) in multiferroic structures by using an external electrical field [1,2]. The following phenomena have been observed and investigated: electrical shift of the FMR frequency in the yttrium iron garnet (YIG) - lead zirconate titanate (PZT), YIG - lead magnesium niobate - lead titanate (PMN-PT), and Ba-hexaferrite – barium strontium titanate (BST) structures on 1-100 MHz under application of electrical fields up to ~10 kV/cm; electrical tuning of the dispersion characteristics, delay time, and the phase of propagating SW in the YIG-PZT and YIG - barium stroncium titanate (BST) structures; electrical switching of nonlinear bistable YIG-PZT resonators with characteristic time less than 1 μs; electrical tuning of the FMR absorption bandwidth in the NiMnGa alloys - PMN-PT single crystal structures on 370 MHz, E-induced switching of magnetization direction in the multiferroic film structures, and the

others. The described phenomena may be used to design novel microwave signal processing devices such as [3-6]: electrically tuned microwave filters, resonators, delay lines, and phase shifters; electrically controlled bistable microwave switchers and logic elements; new kind of electrically writing magnetic memory units. Multiferroic layered structures based devices provide new possibilities to decrease power consumption and increase operation speed, in comparison with traditional magnetically controlled devices.


31

[1] S.Shastry, G. Srinivasan, M.I. Bichurin et al, Phys. Rew. B70, 064416 (2004). [2] G. Srinivasan, Y.K. Fetisov, Ferroelectrics, v. 342, p. 65 (2006). [3] Y.K. Fetisov, G. Srinivasan, Electronics Lett., v. 47, No 19, p.1066 (2005). [4] A.B. Ustinov, G. Srinivasan, Appl. Phys. Lett. V. 93, 142503 (2008). [5] B.J. Lou, M. Liu, N. Sun et al, Adv. Mater. V. 27, p. 4711 (2009). [6] A.B. Ustinov, Y.K. Fetisov, S.V. Lebedev et al, J.Com. Techn. Electr., v. 55, No 12, p. 1416 (2010). Wednesday, 11:00 – 11:30

Thermally-assisted nonlinear dynamics of a nanomagnet

excited by spin transfer torque

Ilya Krivorotov, Xiao Cheng, C. Boone, and J. Zhu

University of California, Irvine

Spin transfer torque from spin-polarized electrical current can excite large-amplitude magnetization dynamics in metallic ferromagnets of nanoscale dimensions. Since the magnetic anisotropy energy of a nanomagnet is comparable to the thermal energy scale, temperature can have a profound effect on the dynamics of a nanomagnet driven by spin transfer torque. We observe unusual types of microwave-frequency nonlinear magnetization dynamics excited by the combined action of alternating spin transfer torque and thermal fluctuations in NiFe/Cu/Co spin valves and CoFeB/MgO/CoFeB magnetic tunnel junctions of nanoscale dimensions [1]. In these dynamics, temperature strongly amplifies the amplitude of GHz-range precession of

magnetization and enables excitation of highly nonlinear dynamic states of magnetization by weak alternating spin transfer torque. We find that this thermally-assisted large-amplitude dynamics of magnetization gives rise to strong enhancement of the rectified voltage generated by nanoscale spin valves in response to alternating spin current, and thus this type of magnetic resonance may find use in sensitive nanometer-scale microwave signal detectors and magnetic field sensors. [1] X. Cheng, C. T. Boone, J. Zhu, I. N. Krivorotov, Phys. Rev. Lett. 105,

047202 (2010). Wednesday, 11:30 – 12:00

Amplification of Spin Waves by the Spin Seebeck Effect

E. Padrón-Hernández, A. Azevedo, and S. M. Rezende

Departamento de Física, Universidade Federal de Pernambuco, Recife, PE

50670-901, Brazil

We present experiments which demonstrate that spin waves propagating in films of yttrium iron garnet (YIG) can be amplified by means of the spin Seebeck effect (SSE). Magnetostatic volume spin-wave packets with frequency in the range 1 – 2 GHz are excited and detected in YIG film strips magnetized in the plane along the strip using standard microstrip antennas. Two different schemes were employed to generate a temperature gradient across the YIG film/GGG substrate, one employs a heater on top of the GGG substrate and the other uses resistive Pt or Mo thin layers deposited on either one or on both

sides of the YIG film/substrate sample heated by currents in the range of 0 - 30 mA. In both schemes when a sufficiently large temperature gradient is established across the YIG film the detected delayed microwave pulse due to the spin wave is amplified. The amplification is attributed to the action of a spin-transfer thermal torque created by spin currents generated through the spin Seebeck effect recently observed in YIG.

1 Amplification occurs if the

temperature gradient exceeds a critical value such that the spin-torque produced by the spin current acting on the magnetization overcomes the relaxation. Amplification gains larger than 20 are observed with a current of 20

2nd


32

mA in a simple YIG/Pt bilayer. The experimental data are interpreted with a spin-wave theory that gives an amplification gain in very good agreement with measurements. The results of this investigation open new possibilities for the use of magnetostatic waves for signal processing in spintronic devices. 1 K. Uchida, H. Adachi, T. Ota, H. Nakayama, S. Maekawa, and E. Saitoh, Appl.

Phys. Lett. 97, 172505 (2010).

Wednesday, 14:00 – 14:30

Spin transfer dynamics in vortex based oscillators

Julie Grollier

1, V. Cros

1, N. Locatelli

1, A. Dussaux

1, A. Khvalkovskiy

1,2, P.

Bortolotti1, V.V. Naletov

3, A. Fukushima

4, G. De Loubens

3, S. Yuasa

4, O.

Klein3, K. Ando

4, and A. Fert

1

1Unité Mixte de Physique CNRS/Thales and Univ. Paris Sud 11, Palaiseau,

France. 2A.M. Prokhorov GPI, Moscow, Russia and Istituto P.M., Torino, Italy.

3Service de Physique de l’Etat Condensé, CEA, Gif-sur-Yvette, France.

4National Institute of Advanced Industrial Science and Technology (AIST),

Tsukuba, Japan.

Given its very rich static and dynamical properties [1], a magnetic vortex excited by a spin polarized current represents not only a model system to study the physical mechanisms of the spin transfer phenomena but also a promising class of powerful and coherent nanoscale microwave sources for telecomunication applications. In metallic systems, the associated microwave emission is weak but very coherent [2]. Here we will first present experimental evidences of high power, low linewidth spin-transfer induced vortex

oscillations in MgO based magnetic tunnel junctions with a large TMR [3]. In addition, unlike spin transfer excitations of quasi uniform modes, the comprehensive comparison between experimental results and models [4] provides for the first time, a clear textbook illustration of the mechanisms of vortex precessions induced by spin transfer. Experiments of phase-locking demonstrate the potential of these MgO based vortex oscillators for self synchronization [5]. Another advantage of vortex based oscillators is that they allow us to tackle the important issue of coupled dynamics in confined nanostructures. In this sense, we will present how the microwave features strongly depend on the vortices parameters (core polarities and chiralities) in double vortex state devices and compare them to analytical predictions and simulations in which a non uniform polarizer is considered. [6]

[1] K. Yu Guslienko, Journal of Nanoscience and Nanotechnology, 8, 2745 (2008) [2] V. Pribiag et al., Nat. Phys. 3, 498 (2007); Q. Mistral et al., Phys. Rev. Lett. 100, 257201 (2008) [3] A. Dussaux et al., Nature Com. 1, 8 (2010) [4] A. Khvalkovskiy et al., Phys. Rev. B 80, 140401 (R) (2009) [5] A. Dussaux et al., Appl. Phys. Lett. 98, 132506 (2011) [6] N. Locatelli et al., Appl. Phys. Lett. 98, 062501 (2011), A. Khvalkovskiy et al., Appl. Phys. Lett. 96, 212507 (2010)


33

Wednesday, 14:30 – 15:00

Analysis of non-linear parameters of spin torque driven

excitations

M. Quinsat,

1,2 J. F. Sierra,

2 D. Gusakova,

2 U. Ebels,

2 M.-C. Cyrille,

1 L. D.

Buda-Prejbeanu,2, E. Monteblanco

2, B. Dieny,

2 V. Tiberkevich,

3 A. Slavin,

3 J.

A. Katine,4 and A. Zeltser

4

1CEA-LETI, MINATEC-campus, 17 Rue des Martyrs, 38054 Grenoble,

France. 2SPINTEC, UMR CEA / CNRS / UJF-Grenoble 1 / Grenoble-INP,

INAC, Grenoble, F-38054, France. 3Department of Physics, Oakland

University, Rochester, MI 48309 USA. 4Hitachi Global Storage Technologies,

3403 Yerba Buena Road, San Jose, California 95135, USA.

Stable limit cycles of the magnetization precession can be established in magneto-resistive devices (spin valves and tunnel junctions) when energy losses through damping are compensated by energy gained through the transfer of spin angular momentum carried by a spin polarized current. The properties and the stability of the corresponding trajectories are characterized by various non-linear parameters where the most important ones are the non-

linear amplitude-phase coupling described by the dimensionless parameter

and the amplitude relaxation rate p [1, 2]. The first one describes the

dependence of the frequency on the oscillation amplitude, and plays an important role in the linewidth broadening and the synchronization of an oscillator to an external signal source. The second parameter defines the time scale over which amplitude fluctuations are damped out, and determines, among other things, the maximum modulation frequency of a spin-torque oscillator. These parameters have been defined within the nonlinear spin

wave theory [1-3] which provides a good theoretical framework for the description of the spin-torque-driven magnetic excitations. Unfortunately, the analytic theory [1-3] does not give the numerical values for these parameters that depend on the specific features of the excited spin wave mode. In our current presentation we demonstrate how the numerical values of these parameters can be evaluated from experimentally measured or numerically

calculated time traces of the signal represented as S(t)=Ao(1+a)cos(t+) [2,

4, 5]. Here a and are, respectively, the fluctuations of the oscillation

amplitude and phase that can be extracted from S(t) using the Hilbert

transformThe autocorrelation function of a and and their power spectral

densities provide direct access to the numerical values of and p. Two

cases of parameter evaluation are considered in our current presentation: (i) experimental study of magnetic tunnel junction oscillators [4], where S(t) is

the magneto-resistive voltage signal V(t) arising from the oscillation of magnetization induced by spin-torque in the oscillator free layer. We compare the experimentally measured signal to the result of macrospin simulations

performed in a single magnetic layer, determine and p, and discuss the

dependence of p and on the experimental parameters, such as bias

current, field, field angle and temperature. (ii) numerical study of spin-torque-induced oscillations in the case when the coupling between a free layer and a synthetic antiferromagnet fixed layer of an oscillator is taken into account. We demonstrate that interlayer coupling caused by spin torque leads to the reduction of the generation linewidth in certain current and field ranges. This reduction is shown to be due to the

reduction of and an increase in p. The coupled excitations, thus, provide a

means to improve the spectral purity of spin torque driven excitations which is an important aspect for technological applications.

[1] J.-V. Kim et al, Phys. Rev. Lett. 100, 017207 (2008); A.N. Slavin et al,

IEEE Trans. Magn 45, 1875 (2009)

[2] T. J. Silva et al, IEEE Trans. Magn. 46, 355 (2010), M.W. Keller et al

Phys. Rev. B 82, 054416 (2010) [3] S. Rezende, et al, Phys. Rev. B 73,

094402 (2006) [4] M. Quinsat et al, Appl. Phys. Lett. 97, 182507 (2010)

[5] L. Bianchini et al, Appl. Phys. Lett. 97, 032502 (2010)

2nd


34

Wednesday, 15:00 – 15:30

Nano-contact spin torque oscillator based magnonic building

blocks

Johan Åkerman, Stefano Bonetti, Yevgen Pogoryelov, Pranaba Muduli, Marco

Madami, Giovanni Carlotti, Gianluca Gubbiotti, and Giancarlo Consolo

Dept. Physics, University of Gothenburg, 412 96 Gothenburg, Sweden. Materials Physics, Royal Institute of Technology, Isafjordsg. 22, 164 40 Kista, Sweden. Dept. Physics, University of Perugia, Via A. Pascoli, 06123 Perugia,

Italy. Dept. Matt. Phys. & E. Eng., U of Messina, 98166 Messina, Italy.

Nano-contact based spin torque oscillators (STOs) operate through the generation of spin waves in a region of the free layer underneath the nano-

contact. The frequency and amplitude of these spin waves can be tuned by the drive current and the applied field strength and the type of spin wave mode can be controlled from propagating to localized as a function of the out-of-plane angle θe of the applied magnetic field as shown both theoretically and using micromagnetic simulations [1-4]. By studying the STO signal as a function of θe, we find that at angles θe below a certain critical angle θcr, two distinct spin wave modes can be excited: a propagating mode, and a localized mode. The experimental frequency, current threshold and frequency tuneability with current of the two modes can be described qualitatively by analytical models and quantitatively by numerical simulations. We also show that the Oersted field strongly affects the current tuneability of the propagating mode at subcritical angles, and it is also the fundamental cause of the mode hopping observed in the time-domain [5].

We argue that the nano-contact STO is the ideal spin wave generator in magnonic circuits and we will describe our efforts in using scanning micro-BLS to directly observe the propagation of such spin waves and the spatial profile of this propagation outside of the nano-contact region. In addition we suggest a number of magnonic building blocks, all based on spin torque driven nano-contact oscillators, that can act as spin wave gates, manipulators and detectors.

[1] A. Slavin and V. Tiberkevich, Phys. Rev. Lett. 95, 237201 (2005). [2] G. Consolo, B. Azzerboni, G. Gerhart, G. A. Melkov, V. Tiberkevich, and A. N. Slavin, Phys. Rev. B 76, 144410 (2007). [3] D. V. Berkov and N. L. Gorn, Phys. Rev. B 76, 144414 (2007). [4] G. Consolo, B. Azzerboni, L. Lopez-Diaz, G. Gerhart, E. Bankowski, V. Tiberkevich, and A. N. Slavin, Phys. Rev. B 78, 014420 (2008).

[5] S. Bonetti, V. Tiberkevich, G. Consolo, G. Finocchio, P. Muduli, F. Mancoff, A. Slavin, and Johan Åkerman, Phys. Rev. Lett. 105, 217204 (2010). Wednesday, 16:00 – 16:30

Control of spin-wave emission characteristics of spin-torque

nano-oscillators

Vladislav E. Demidov

1, Sergei Urazhdin

2, and Sergej O. Demokritov

1

1Institute for Applied Physics, University of Muenster, Muenster, Germany.

2Department of Physics, West Virginia University, Morgantown, USA

In this talk I review our recent achievements in experimental investigations of

spin-wave emission by spin-torque nano-oscillators (STNOs) and studies on the control of the emission characteristics. The experiments were performed by using micro-focus Brillouin light scattering (BLS) spectroscopy, which allowed recording of two-dimensional spin-wave intensity patterns with the spatial resolution of about 250 nm. The studied STNOs were lithographically-prepared point contacts with dimensions below 100 nm made on an extended permalloy film. We show that STNOs emit spin waves in a form of highly-directed beams perpendicular to the direction of the static magnetic field. The efficiency of


35

emission is strongly affected by the nonlinear frequency shift. We demonstrate

that the propagation length of the emitted spin waves can be controlled by nonlinear frequency conversion, as well as by modification of the internal magnetic fields under the point contact using micro-magnets built into STNO devices.

S. O. Demokritov and V. E. Demidov, IEEE Trans. Mag. 44, 6 (2008).

V. E. Demidov, S. Urazhdin and S. O. Demokritov, Nature Materials 9, 984

(2010). V. E. Demidov et al., Phys. Rev. B 83, 060406(R) (2011).

Wednesday, 16:30 – 17:00

Using magnons to probe spintronic materials properties

R. D. McMichael1, Meng Zhu

1,2, and Konrad Aschenbach

1,2

1National Institute of Standards and Technology.

2Maryland Nanocenter,

University of Maryland

This talk will describe experiments that use the interaction of spin waves with spin-polarized currents to determine the drift velocity of the magnetization and the spin polarization of current in ferromagnetic metals. In ferromagnetic metals, the majority and minority (up-spin and down-spin) electrons carry different amounts of charge current. Each electron also carries a magnetic moment, and this fact implies that there is also a net flow of magnetic moment associated with current in magnetic metals. For spin waves interacting with a current with polarization P, a detailed analysis leads to a simple picture where the spin waves propagate in a medium that moves with a magnetic moment

drift velocity u. Expressions for u and P are

B

s

;2

J Jg PP

e M J J

u J .

Here, B / 2g is the magnetic moment of an electron, J/e is the electron

current density and Ms is the moment density of the ferromagnet. The situation for current driven domain walls is more complicated. For spin waves, the velocity u adds to the spin wave group velocity vg, leading to a Doppler

shift of the spin wave dispersion ( ) · k u k .

In a seminal paper [1], Vlaminck and Bailleul introduced a spin wave transmission technique that measured u and P in Ni80Fe20 wires. I will

describe measurements at NIST, where the spin wave Doppler method has

been applied to several systems of interest:

measurements of the temperature dependence of polarization in Permalloy, [2]

measurements of polarization up to 95 % in (CoFe)1-xGax Heusler-like alloys [3] and

the effects of Gd doping on u and P in Permalloy that point to the

role of spin flip scattering in reducing P. This work has been supported in part by the NIST-CNST/UMD-NanoCenter Cooperative Agreement.

[1] V. Vlaminck and M. Bailleul, Science, 322, 410 (2008); R. D. McMichael

and M. D. Stiles, Science, 322, 386 (2008).

[2] M. Zhu, C. L. Dennis, and R. D. McMichael, Phys. Rev. B Rapid Comm.

81, 140407(R) (2010)

[3] M. Zhu, B. D. Soe, R. D. McMichael, M. J. Carey, S. Maat, and J. R. Childress, Appl. Phys. Lett., 98, 072510 (2011).

2nd


36

Wednesday, 17:00 – 17:30

Magnon Spintronics

Burkard Hillebrands

1, Andrii V. Chumak

1, Alexander A. Serga

1, M. Benjamin

Jungfleisch1, Christian W. Sandweg

1, Yosuke Kajiwara

2, and Eiji Saitoh

2

1Fachbereich Physik and Forschungszentrum OPTIMAS, University of

Kaiserslautern, 67663 Kaiserslautern, Germany.2Institute for Materials

Research, Tohoku University, Sendai 980-8577, Japan.

Spintronics is concerned with the development of devices which exceed the performance and energy efficiency of conventional charge-based electronics by exploiting the electron's spin degree of freedom. Spin angular momentum, which is the information carrier in spintronics, can be transferred not only by

the flow of electrons, but also by magnons: the quanta of spin waves (collective excitations of the spin lattice of a magnetic material). This opens a new research direction: magnon spintronics, a sub-field of spintronics, in which information is transferred and processed using magnons. In my talk I will concentrate on the main construction blocks of a magnon spintronics device: (1) converters for information transfer between spin or charge of electrons and magnons, (2) magnon conduits, and (3) physical phenomena allowing information processing by magnons. Very promising convertors for magnon spintronics are based on the spin pumping effect (which transforms spin waves into pure spin currents) and the inverse spin Hall effect (iSHE) (which converts spin currents into charge currents). We have intensively studied magnetic insulator yttrium iron garnet (YIG) – nonmagnetic platinum (Pt) structures. We have shown that different dipolar spin-wave modes have different spin pumping efficiencies [1].

Additionally, we have investigated spin pumping for purely exchange sub-micron wavelength magnons injected in the system using parametric pumping [2]. The effect of a direct transfer of spin-angular momentum into the Pt as a result of three-magnon scattering in YIG has been observed. Studies of the temporal behavior of the iSHE-voltage in YIG/Pt structures [3] demonstrate that the iSHE voltage is distinctly different from the temporal evolution of the directly excited spin-wave mode from which it originates. This is due to the excitation of long-lived secondary spin-wave modes localized at the insulator-metal interface. Magnon conduits will be discussed using the example of meso-sized YIG-based and micro-sized Permalloy-based magnonic crystals (MCs). A MC is an artificial media with spatially periodic variation of its magnetic properties. It can serve as a magnon conduit combined with information processing elements

allowing, e.g., filtering or phase shifting. Versatile magnon physics provides unique opportunities for magnon spintronics. As an example, I will show our experimental results where all-linear spectral transformation, including frequency inversion and time reversal, has been realized by a dynamic magnonic crystal [4]. [1] C.W. Sandweg, et al., Appl. Phys. Lett. 97, 252504 (2010).

[2] M.B. Jungfleisch, et al., Temporal behavior of the inverse spin Hall voltage

in a magnetic insulator-nonmagnetic metal structure, arXiv:1011.0889. [3] C.W. Sandweg, et al., Spin pumping by parametrically excited exchange

magnons, arXiv:1103.2229v1 [4] A.V. Chumak, et al., Nat. Commun. 1, 141; doi: 10.1038/ncomms1142

(2010).


37

Poster Session

P1. Spin current absorption in thin metal films measured

through ferromagnetic resonance

A. Ghosh

1, S. Auffret

1, U. Ebels

1, and W. E. Bailey

1,2

1SPINTEC, UMR CEA/CNRS/UJF–Grenoble 1/Grenoble–INP, INAC,

Grenoble F-38054, France. 2Department of Applied Physics and Applied

Mathematics, Columbia University, New York,

A spin polarized current entering a ferromagnet (FM) transfers spin angular momentum to the ferromagnet. This phenomenon, known as spin transfer

torque (STT), results in either a magnetization reversal or in steady magnetization oscillations as has been observed in a variety of experiments. A question of fundamental interest is the length scale over which the spin momentum is transferred. Stiles and Zangwill [1] have predicted that the angular momentum is transferred completely to the FM within a few lattice constants. Up to now, few experiments have been performed to probe this spatial dependence in detail. Here we show that a convenient method to probe spin current absorption is via spin pumping in FM1/Cu/overlayer thin film heterostructures [2]. When undergoing ferromagnetic resonance (FMR), a pure spin current can be pumped out of a ferromagnetic thin film FM1 that can be absorbed by a non-resonating ferromagnetic FM2 overlayer or by a non-magnetic NM overlayer. This absorption results in an additional nonlocal

damping for FM1 undergoing ferromagnetic resonance. The thickness

dependence of the enhanced damping (t) with overlayer thickness t

provides a measure of the thickness dependent spin current absorption at the

Cu/NM(t) or Cu/FM2(t) interface. The damping parameter and the

corresponding Gilbert damping G=Ms of FM1 is extracted from ferromagnetic resonance (FMR) measurements using an in-plane field swept (0-1T) broadband (0-24GHz) coplanar waveguide FMR technique with field modulated lock-in detection [3]. Here we investigate the spin current absorption for different ferromagnetic (Ni81Fe19, Co60Fe20B20, Co), antiferromagnetic AFM (Ir20Mn80) and nonmagnetic (Pt, Pd, Ru) overlayer materials in FM1/Cu/overlayer heterostructures, where FM1 is either Ni81Fe19(10nm) or Co(8nm). For all ferromagnetic FM2 overlayers a sharp increase of the enhanced damping is observed up to 1.1nm, above which the enhanced damping remains constant. This indicates that the spin current absorption by a

ferromagnet (FM2) has a cut-off-like functional form and its short cut-off length is in good agreement with the predictions made by Stiles. A similar type of absorption characteristics was observed for the antiferromagnet overlayer Ir20Mn80 with 1.5nm of cutoff length. In contrast to this, all non-magnetic overlayers reveal an exponential increase of the enhanced Gilbert damping, whose characteristic length after theory corresponds to the spin diffusion

length sdl [4]. From best fitting we found: sdlPt

=1.4, sdlPd

=4.74, sdlRu

=4.39. The difference in the nature of absorption characteristics of ferromagnets and nonmagnets suggest that the spin current absorption in ferromagnets is indeed governed by spin momentum transfer whereas in non-ferromagnets it is governed by spin flip scattering. [1] M. D. Stiles, et al., Phys. Rev. B 66, 014407 (2002).

[2] Y. Tserkovnyak, et al., RMP 77, 1375 (2005).

[3] A. Ghosh, et al., Appl. Phys. Lett. 98, 052508 (2011).

[4] J. Foros, et al., J. Appl. Phys. 97, 10A714 (2005).

2nd


38

P2. Vortex dynamics in magnetic disks

Alexandre M. Gonçalves, Naiara Y. Klein, and Luiz C. Sampaio

Centro Brasileiro de Pesquisas Físicas (CBPF), Rio de Janeiro, RJ, Brazil

We have investigated the magnetization dynamics and the spin wave generation in Permalloy disks. The disks have the appropriate diameter (d) and thickness (t) to exhibit a magnetic vortex, d t from 20 to 40 nm. It is known from recent experiments that the vortex core magnetization dynamics, including the magnetization reversal, can be induced applying a magnetic field or passing a spin polarized current through the disk. According to our simulations using the LLG equation, the vortex core magnetization

reversal generates spin waves with radial propagation. In our work we have used a current (DC and AC) passing through the disk and measure the electrical resistance. We have grown Permalloy disks using electron beam lithography and lift-off process. Several Au pads contacts were deposited in appropriated places on the disk to measure the vortex core movement, its magnetization reversal and the spin wave propagation. We will show details on the sample fabrication process, the experimental setup and how a magnetic vortex can be used to generate spin waves in magnonic devices.

P3. Spin-electromagnetic wave ferrite-ferroelectric

nonlinear phase shifters

Alexey Ustinov, and Boris Kalinikos

Saint Petersburg Electrotechical University, 197376, Saint Petersburg, Russia

In recent years there is a strong interest to ferrite-ferroelectric (FF) structures (see e.g. [1]. In particular, the linear properties of spin-electromagnetic waves (SEWs) propagating in FF layered structures have been studied and a number of linear ferrite-ferroelectric devices have been designed and suggested [2-4]. This work reports the first experimental results on a nonlinear FF device, namely, SEW nonlinear phase shifter. A principle of operation of the device is based on the dual control of the phase shift of the hybrid spin-electromagnetic waves propagating in the FF bilayer. The specific experiments were carried out for the phase shifter structure similar to that described in [3]. The layered structure was composed of 5.7-μm-thick single

crystal yttrium iron garnet film and a 500-μm-thick barium strontium titanate slab. Two microstrip transducers separated by 8 mm were used for the excitation and detection of the SEW. A bias voltage in the range of U = 0-1000 V was applied across the BST slab. The prototype device was placed between the poles of electromagnet. The bias magnetic field in the range of H = 1100-1400 Oe was applied in-plane of the YIG film parallel to the antennae. In the experiment, S-parameters as a function of frequency f and as a function of input microwave power Pin were measured for different H and U. The device demonstrated a dual-function performance with a nonlinear phase shift up to 140 degree for Pin = 15 dBm and electric field induced differential phase shift up to 330 degree for U = 1000 V. The nonlinear phase shift increased with frequency whereas the differential phase shift decreased with frequency. Therefore, the nonlinear phase shift and electric field induced differential phase shift are competing characteristics for the surface SEW nonlinear

phase shifters. The device could find different applications. In particular, it could be used for development of the microwave logic gates, nonlinear interferometers, and nonlinear directional couplers. This work was supported in part by the Russian Foundation for Basic Research, the Ministry of Education and Science of Russia, and by the grant of the President of Russian Federation.


39

Fig. 1 Schematic of dynamic magnonic crystal system (left) and experimental transmission characteristics (right). The dotted line shown in the transmission data corresponds to the „off‟ state, the solid line the „on‟ state. The latter features a band gap centred on frequency fa

Fig. 2 Experimental data showing secondary signal

spectra as the carrier frequency of the incident signal is varied. Coupled wave frequencies are related by inversion about fa.

1. U. Ozgur et al., "Microwave ferrites, part 2: passive components and

electrical tuning," J. Mater. Sci.: Mater. Electron. 20, 911 (2009).

2. V. E. Demidov et al., "Dipole-exchange theory of hybrid electromagnetic-spin waves in layered film structures," J. Appl. Phys. 91, 10007 (2002).

3. A. B.Ustinov et al., "Ferrite-ferroelectric hybrid wave phase shifters," Appl. Phys. Lett. 90, 031913 (2007).

4. A.B. Ustinov et al., "Q-factor of dual-tunable microwave resonators based on yttrium iron garnet and barium strontium titanate layered structures," J. Appl. Phys. 103, 063908 (2008).

P4. The dynamic magnonic crystal: a window into new wave

phenomena

Alexy D. Karenowska

1, Andrii V. Chumak

2, Vasil S. Tiberkevich

3, Alexander A.

Serga2, John F. Gregg

1, Andrei N. Slavin


2

1Department of Physics, University of Oxford, Oxford, United Kingdom. 2Fachbereich Physik and Forschungszentrum OPTIMAS, Technische

Universität Kaiserslautern, Kaiserslautern, Germany. 3Department of Physics,

Oakland University, Rochester, MI, United States

A magnonic crystal [1-6] is a spin-wave transmission structure featuring an „artificial lattice‟ formed by a wavelength-scale spatial modulation in its magnetic properties. Like other artificial crystals, for example optical photonic crystals [7-9], the transmission spectra of magnonic crystals typically include band gaps; frequency intervals over which wave propagation is prohibited. In this paper, we present the results of a series of investigations into spin-wave propagation in a dynamic magnonic crystal which can be switched from a

spatially uniform state with a trivial transmission spectrum („off‟), to a spatially modulated state with a well defined band gap („on‟) (Fig. 1). We show that this dynamic functionality, which is unique in the wider context of artificial crystal systems, allows us to observe interesting new physical phenomena. In particular, we demonstrate that if the dynamic magnonic crystal undergoes a rapid transition from „off‟ to „on‟ whilst an incident spin wave having a frequency lying within the band gap is excited inside it, this wave becomes coupled to a secondary counter-propagating wave, generally of a different

2nd


40

frequency, and energy oscillates between the two [5, 6]. We explore the features of this coupling phenomenon experimentally and theoretically and establish that its underlying physics reveals a fundamental result of general wave dynamics. The incident and secondary wave frequencies are shown to be related by inversion about the magnonic crystal‟s band-gap centre frequency fa (Fig. 2). We offer experimental confirmation that this feature of the coupling effect implies that it can be used to perform all-linear frequency conversion and time reversal of signals; functionalities of considerable technological significance [5 [1] A. V. Chumak et al., J. Phys. D 42, 205005 (2009).

[2] K-S. Lee et al., Phys. Rev. Lett. 102, 127202 (2009).

[3] Z. K. Wang et al., Appl. Phys. Lett. 94, 083112 (2009).

[4] G. Gubbiotti et al., J. Phys. D 43, 264003 (2010).

[5] A. V. Chumak et al., Nature. Commun. 1, 141 (2010).

[6] A. D. Karenowska et al., submitted (2010). [7] J. Bravo-Abad and M. Soljačić, Nature 6, 799 (2007).

[8] E. J. Reed et al., Phys. Rev. Lett. 90, 203904 (2003).

[9] S-Y. Lin et al., Science 282, 274 (1998).

P5. Generation of Dark and Bright Spin Wave Envelope Soliton

Trains Through Self-Modulation Instability in Magnonic

Crystals

Andrey Drozdovskii, Alexey Ustinov, and Boris Kalinikos

St.Petersburg Electrotechnical University

Envelope solitons in nonlinear dispersive media have the potential for applications in microwave and optical signal processing. Two types of envelope solitons, bright and dark, may propagate in nonlinear dispersive media. There are several ways to produce envelope solitons, namely, from a pulsed bright or dark initial perturbation, from a single-frequency input excitation (self-modulation instability), and from double-frequency input excitation (induced modulation instability). The aim of this work is to study the possibility of the formation and propagation of bright and dark envelope solitons in magnonic crystals due to the self-modulation instability (SMI) effect. The excitation and detection of spin-wave signals was performed utilizing a common delay-line structure with 2-mm long, 50-μm wide, short-circuited input and output microstrip antennae. The distance between the antennae was 5.2 mm. Experimentally investigated magnonic crystal sample had a thickness of

10.3 μm, a width of 2 mm, and a length of 35 mm. Grooves with a depth of 3.3 μm, a width of 50 μm, and a period of 400 μm were etched over the entire width of the yttrium iron garnet film waveguide perpendicular to its longer axis. The experimental sample was placed in a homogeneous static magnetic field of 930 Oe. The field was directed in parallel to the plane of the magnetic periodic structure along the long side of the magnonic crystal. Thus, the input antenna excited the backward volume spin waves. The self-modulation instability of spin waves was observed in the spectral regions with a strong dispersion, which were situated near the stop-bands caused by the Bragg resonances. It appeared in the narrow frequency bands positioned near the first three stop-bands caused by the Bragg resonances, in a limited range of microwave input power. For example, the self-modulation instability was observed in the power range from 21.5 dBm to 27 dBm for

frequency band of 34 MHz near the centre of the second gap. The self-modulation instability of spin waves was detected in the first three stop-bands. A well-developed SMI, which led to the bright soliton train formation was detected near the second stop-band. This formation of the bright solitons occurred at the frequencies corresponding to the left (low-frequency) slopes of the stop band, where the group velocity of the spin waves increases rapidly with frequency. In other words, the formation of bright solitons was observed in the regions of strong positive dispersion. In contrast, the dark soliton formation was observed at the left slopes of the stop-bands where the


41

dispersion was negative. The self-modulation instability and formation of

solitons in the spectral intervals situated between the stop-bands were not observed in the broad power interval of 1–30 dBm provided by the experimental set-up. This work was supported in part by Russian Foundation for Basic Research, the Ministry of Education and Science of Russia, and by the grant of the President of Russian Federation.

P6. Photo-magnonics: Spin-wave localization in magnonic

crystals

Benjamin Lenk, Fabian Garbs, Henning Ulrichs*, and Markus Münzenberg

Physikalisches Institut, Georg-August-Universität Göttingen, Germany,

*current address: Institut für Angewandte Physik, Westfälische Wilhelms-Universität Münster, Germany

All-optical femtosecond laser experiments allow the excitation of spin-waves. Over the last years, it became valuable novel method to study spin-waves and their relaxation paths. Laser pulses with a duration of 60 fs from a Ti:Sa regenerative laser system are used for optical excitation. Local single spin excitations decay after laser excitation into spin waves of lower energy and dipolar surface modes with well defined k-vector can be excited. In the first part I want to enlighten in an overview the intrinsic spin-flip processes involved

and how the spin-waves are subsequently excited. A spin-flip rate el-sp together with intrinsic correlated spin fluctuations gives us a reasonable understanding of the ultrafast demagnetization [1]. As a result laser excitation allows creating well defined modes with a specific

k-value all-optically. Using focused ion beam patterning, a two dimensional periodic modification of the material is imposed with distances in the spin-wave length range and allows the control of the localization of the spin-wave modes in such magnonic crystals [2]. The resulting modes depend strongly on the strength of the magneto-static potential at around each hole site. This is much different to photonic crystals. It leads to mode localization. However for low filling fractions also delocalized Bloch states at the Brilluoin zone can be found [3]. One example for a distinct modification of the magnonic periodic structure is a line defect that can function as a wave guide inside the magnonic gap region and can be further functionalized. A study of these wave guides will allow eventually specifically designing the properties of spin-wave computing devices.

[1] Thermal mechanisms in laser-induced femtosecond spin dynamics, U. Atxitia, O. Chubykalo-Fesenko, J. Walowski, A. Mann, and M. Münzenberg, Phys. Rev. B 81, 174401 (2010). [2] The building blocks of magnonics (review), B. Lenk, H. Ulrichs, F. Garbs, M. Münzenberg, arXiv:1101.0479v1 [3] Magnonic spin-wave modes in CoFeB antidot lattices H. Ulrichs, B. Lenk, and M. Münzenberg, Appl. Phys. Lett. 97, 092506 (2010). Website: http://www.uni-goettingen.de/de/124076.html

P7. Magnetization Dynamics of Ni81Fe19/Cu Films

Electrodeposited on Copper Microwire

B. G. Silva, D. E. González-Chávez, J. Gomes Filho, and R. L. Sommer

Centro Brasileiro de Pesquisas Físicas, Rua Dr. Xavier Sigaud 150, Urca, Rio

de Janeiro, Brasil

Electrodeposited cylindrical magnetic films of NiFe, NiFeRu, NiFeMo, CoP, CoNiFe, etc have been deposited on a non-magnetic inner core conductor (Cu, BeCu, Ag, etc) in order to produce magnetoimpedance based sensors or to application in other fields. Such structures are good candidates to exhibit very high magnetoimpedance ratios and very interesting Z vs. H behaviors. Planar structures made of sandwiched FM/M/FM layers were found to exhibit


http://arxiv.org/abs/1101.0479

http://apl.aip.org/resource/1/applab/v97/i9/p092506_s1

http://www.uni-goettingen.de/de/124076.html

2nd


42

even better MI rations, although smaller than the theoretical limit of 3000 percent. In this work, copper microwires with diameter of 100um were uniformly recovered with NiFe/Cu multilayer of varying thickness. The depositions were made on the potenciostatic mode, at room temperature, with no agitation and pH = 2.8. All the electrodeposition essays were produced on a Autolab potenciostat. The static magnetic properties for these samples were investigate with VSM magnetometer and Magnetic Force Microscopy. The magnetization dynamics and magnetoimpedance were studied with a coaxial wave guide attached to a ZVA24 Rohde & Schwarz Network Analyzer in the frequency range 10MHz-6GHz. The magnetoimpedance and permeability results are discussed in terms of the anisotropies and the static magnetic properties observed in the samples. Keywords: magnetoimpedance, permeability, magnetization dynamics. Work supported by CNPq and CAPES.

[1] Quemper, J.-M. et al., Sensors and Actuators, v.74, pp.1-4, (1999). [2] F. L. Machado et al., J. Appl. Phys. 75, 656 (1994); 73, 6387 (1993). [3] M. Carara, K. D. Sossmeier. A.D.C. Viegas, J. Geshev, H. Chiriac and R. L. Sommer. J. Appl. Phys. 98, 033902 (2005).

P8. Terahertz Band Gaps in Generalized Fibonacci

Quasiperiodic Magnonic Crystals

Carlos H. O. Costa

1, Manoel S. Vasconcelos

2,*, and Eudenilson L.

Albuquerque3

1Departamento de Física Teórica e Experimental, Universidade Federal do Rio Grande do Norte, 59072-970, Natal-RN, Brazil.

2Escola de Ciências e

Tecnologia, Universidade Federal do Rio Grande do Norte, 59072-970, Natal-RN, Brazil.

3Departamento de Biofísica e Farmacologia, Universidade Federal do Rio Grande do Norte, 59072-970, Natal-RN, Brazil.

Magnetic periodic layered structures have been studied for more than a decade, including the discovery of the giant magneto-resistance effect in a three layer system containing magnetic and nonmagnetic layers [1]. However, magnonic crystals (MCs), the magnetic counterpart of photonic crystals (PCs), were only recently have gained detach with the experimentally works of Kruglyak et al. [2]. They have observed that, similar to PCs, the spectrum of MCs is strongly affected by the presence of magnonic band gaps (MBGs), in which magnon propagation is forbidden. In such systems the magnons (quantized spin waves) move through these crystals, analogous to photons in

PCs. In MCs, spin waves are the quasiparticles that are responsible by the transport and process of information. Considerably effort, theoretical and experimental, has been made to investigate the MCs in the last years. However, few efforts had been done to investigate magnonic structures in exchange regime. The principal aim of this work is try to fill this gap. Therefore, we investigate MBGs, in the terahertz (THz) frequency range, in MCs organized in periodic and quasiperiodic generalized Fibonacci fashion. Due to the quasiperiodic design, this last structure is called by magnonic

quasicrystals (MQCs). The theoretical model adopted here is based on the Heisenberg Hamiltonian in the exchange regime, together with a transfer-matrix treatment within the random-phase approximation (RPA) [3]. In this regime, the exchange terms of the magnetic layers play the same role of electric permittivity in PCs. For periodic arrangements the bulk band structure is analogous to those found in PCs, while for quasiperiodic multilayers it

presents additional pass bands similar to those found in doped semiconductor materials. Corresponding author: *[email protected] [1] M. N. Baibich, J. M. Broto, A. Fert, F. Nguyen Van Dau, and F. Petroff, Phys. Rev. Lett. 61, 2472 (1988).

[2] V.V. Kruglyak, S.O. Demokritov and D Grundler, J. Phys. D: Appl. Phys. 43, 264001 (2010).

[3] C.H.O. Costa, P.H.R. Barbosa, F.F. Barbosa Filho, M.S. Vasconcelos and E.L. Albuquerque, Solid State Commun. 150, 2325 (2010).


43

P9. Schottky Barrier in ZnO Electrodeposited on Pt and Ni

Films

Carolina F. Cerqueira and Luiz C. Sampaio

Centro Brasileiro de Pesquisas Físicas, Rua Dr. Xavier Sigaud 150, Urca, Rio

de Janeiro, Brasil

Zinc oxide (ZnO) is a semiconductor material with a wide band gap at room temperature. It has great applicability in optoelectronics and spintronics. In the interface between layers of semiconductor and ferromagnetic materials can be induced interesting effects like the appearance of a spin polarized current. This work presents the fabrication process and the characterization of ZnO/Pt

thin Films that exhibits Schottky barrier. Platinum films were grown by sputtering into a silicon substrate and the ZnO film was produced by electrodeposition. The crystalline structure with hexagonal symmetry of ZnO electrodeposited was confirmed by X-ray diffraction and by electron microscopy. Electrical contacts were made between platinum and ZnO films, thus allowing IxV measurements. These measurements were fitted using the thermionic model. It enabled the calculation of the barrier height and the factor of ideality of the Schottky contact. The values for the barrier height were between 0.84 eV e 1.02 eV. A nickel layer was added between the zinc oxide and platinum films. Magnetic and transport measurements have been made in films ZnO /Ni/Pt.

P10. Large Area Molecularly Assembled Nanopatterns for

Devices (LAMAND)

Claudia Simao

1, Achille Francone

1, Nikolaos Kehagias

1, Richard A. Farrell

2,3,4,

Marc Zelsmann5, Mustapha Chouiki

6, Rainer Schoeftner

6, Vincent Reboud

1,

Justin D. Holmes2,3,4

, Michael A. Morris2,3,4

and Clivia Sotomayor Torres1,7

1Phononic and Photonic Nanostructures Group, Catalan Institute of

Nanotechnology (CIN2-CSIC), Campus Bellaterra - Edifici CM3, 08193-Bellaterra (Barcelona), Spain.

2Centre for Research on Adaptive

Nanostructures and Nanodevices (CRANN), Trinity College, University of Dublin, Dublin, Ireland.

3Tyndall National Institute, University College Cork,

Cork, Ireland. 4Materials Chemistry Section, Department of Chemistry,

University College Cork, Cork, Ireland. 5LTM-CNRS, 17 rue des Martyrs

38000, Grenoble, France. 6Profactor GmbH, Functional Surfaces and

Nanostructures, Steyr-Gleink, Austria. 7Catalan Institute for Research and

Advanced Studies ICREA, 08010 Barcelona, Spain.

Nanoimprint lithography (NIL) is a top-down parallel lithographic technique capable of creating patterns with sub 50 nm resolution by mechanically deforming a polymeric resist layer in conjunction with a thermal

1 and/or a ultra-

violet curing step2. This technique can be extended to inorganic polymer

systems such as poly-silsesquioxanes (PSSQ) for fabricating nano-arrays and 3D structures. Silsesquioxane nanostructures have found uses in many applications recently, most notably as a direct write negative tone e-beam resist for patterning nanowires

3 and low-k dielectric insulation materials

4.

Previous work on aligning (by graphoepitaxy) block copolymer nano-patterns within electron beam patterned SSQ type templates have shown that linear and concentric hexagonal arrays of PS-b-PMMA lamallae patterns can be

assembled with precision5. The combination of using a neutral brush layer at

the base and a HSQ sidewall allowed for the researchers to create hexagonal arrays with up to 2 concentric rings of PMMA with low defect content. Extremely thin layers (~ 2 nm) of hydrogen silsesquioxane have also been written by electron beam methods to create chemical patterns (14 nm half-pitch) to align and register PS-b-PMMA patterns

6. The incorporation of metal

nanoparticles in these BCP can work as hard masks for photolithography but can also bring magnetism to the fabricated nanostructures, interesting for magnonic devices.

2nd


44

In this paper we report on the patterning (figure 1) of poly-silsesquioxane (PSSQ) films by reverse UV nano-imprint lithography (RUVNIL) technique

7

and investigate the self-assembling properties and polymer flow/de-wetting phenomena of cylinder forming polystyrene-block-polymethylacrylate (PS content 0.72, 67.0 kg/mol) block copolymer films following thermal annealing (figure 2). [1] Chou, S. Y.; Krauss, P. R.; Renstrom, P. J. Science 1996, 272, (5258), 85-87 [2] Bailey, T.; Choi, B. J.; Colburn, M.; Meissl, M.; Shaya, S.; Ekerdt, J. G.; Sreenivasan, S. V.; Willson, C. G. Journal of Vacuum Science & Technology B 2000, 18, (6), 3572-3577. [3] Namatsu, H.; Takahashi, Y.; Yamazaki, K.; Yamaguchi, T.; Nagase, M.; Kurihara, K. Journal of Vacuum Science & Technology B 1998, 16, (1), 69-76.

[4] Kohl, A. T.; Mimna, R.; Shick, R.; Rhodes, L.; Wang, Z. L.; Kohl, P. A. Electrochemical and Solid State Letters 1999, 2, (2), 77-79. [5] Yamaguchi, T.; Yamaguchi, H. Advanced Materials 2008, 20, (9), 1684 [6] Cheng, J. Y.; Rettner, C. T.; Sanders, D. P.; Kim, H. C.; Hinsberg, W. D. Advanced Materials 2008, 20, (16), 3155-3158. [7] N. Kehagias, V. Reboud, G. Chansin, M. Zelsmann, C. Jeppesen, C. Schuster, M. Kubenz, F. Reuther, G. Gruetzner and C. M. Sotomayor Torres, Nanotechnology, 18, 175303, (2007)

Fig. 1 Top view scanning electron microscope image of PSSQ template for

graphoepitaxy

Fig. 2 PS-PMMA micro-droplet formation (on patterned PSSQ substrate) by

controlled de-wetting using the via as a sink for polymer flow and adjusting via width/spacer dimensions

The authors would like to acknowledge the following sources of funding which supported this work: NaPANIL (FP7-CP-IP 214249), LAMAND (FP7-NMP-2009-245565), SFI grant 03-IN3-I375, SFI CRANN CSET grant. The authors are grateful to Intel Ireland for access to microscopy facilities and continuous support.


45

P11. Magnetization dynamics of Py/Ag multilayered films

studied with vector network analyzer magnetometry

D.E. González-Chávez

1, T. L. Marcondes

1, M.A. Corrêa

2, A. M. H. de

Andrade3, and R. L. Sommer

1

1CBPF, Rio de Janeiro, RJ, Brazil.

2EC&T, UFRN, Natal, RN, Brazil.

3CCNE,

UFSM, Santa Maria, RS, Brazil

Recent technological applications of magnetic materials as magnetic recording, spin toque oscillators, field sensors, etc demand the use of increasingly high operating frequencies. As a consequence, the magnetization dynamics has become a paramount issue in the study and characterization of the materials and structures involved. The physical processes associated to

the high frequency (HF) magnetic behavior include the excitation of the sample by HF and DC magnetic fields, and subsequent magnetic relaxation characteristic to the magnetic material, vector network analyzer magnetometry (VNAM) provides a excellent tool for broadband measurements of this phenomenon. In this work we present dynamic magnetic characterization of Permalloy/Silver [Py(10nm)/Ag(tAg )] × n multilayered films with tAg = 0,5nm, 1,0nm, 2,5nm and n = 20, 50. All VNAM were performed in the frequency range 10 MHz - 10GHz. Static properties were also studied by VSM magnetometry. High frequency measurements were made using inductive methods based on a waveguide attached to a Rhodes&Shwarz ZVA24 vector network analyzer (VNA). Broadband permeability measurements shows typical ferromagnetic resonance behavior, Dispersion relations and FRM linewidth were calculated from measured data, this results are compared with numerically calculated data. The results are discussed in terms of the

anisotropies and magnetic microstructure observed in the samples.)

P12. Low-temperature spectroscopy on magnonic devices in

perpendicular fields

T. Schwarze, F. Brandl, R. Huber, G. Duerr, S. Neusser, and Dirk Grundler


Germany

In recent years the field of collective spin excitations in nanopatterned ferromagnets gained great interest both scientifically and technologically [1]. In

particular magnonic crystals hold great promises in controlling and manipulating the propagation of spin waves. Recent studies on 1D and 2D periodically patterned ferromagnets were performed in-plane magnetic fields at room temperature [2,3]. In order to get a deeper understanding of the underlying physics we have developed further the all-electrical spin-wave spectroscopy (AESWS) [3] and implemented it in a cryogenic low-temperature setup. The setup allows us to study a broad frequency range up to 40 GHz and vary the sample temperature from 4 to 400 K. The external magnetic field of up to 2.5 T is applied along the growth direction of thin-film devices. The ability to probe spin waves with an out-of-plane magnetic field and in a wide temperature range leads to new insights concerning demagnetization-field and damping effects. We have investigated permalloy thin films and, recently, an antidot lattice. We report on the experimental setup and discuss the temperature dependent variation of the resonance fields and frequencies, the

resonance linewidths, the Gilbert damping , and the spin-wave propagation velocities. The research leading to these results has received funding from the European Community‟s Seventh Framework Programme (FP7/2007-2013) under Grant Agreement no. 228673 and the German Excellence Cluster ‟Nanosystems Initiative Munich‟. [1] S. Neusser and D. Grundler, Adv. Mater. 21, 2927 (2009); V.V. Kruglyak et al., J. Phys. D: Applied Physics 43, 264001 (2010); and references therein.

2nd


46

[2] G. Gubbiotti et al., J. Phys. D: Applied Physics 43, 264003 (2010). [3] S. Neusser et al., Phys. Rev. Lett. 105, 067208 (2010).

P13. Properties of magnetic nanodots with perpendicular

anisotropy

Erico Novais

1, Pedro Landeros

2, Andreia Barbosa

3, Maximiliano Martins

3,

Flavio Garcia4, and Alberto Guimarães

1

1Centro Brasileiro de Pesquisas Físicas, 22290-180, Rio de Janeiro, RJ,

Brazil. 2Dept. de Física, Universidad Téecnica Federico Santa Maria,

Valparaiso, Chile. 3Centro de Desenvolvimento da Tecnologia Nuclear,

31270-901, Belo Horizonte, MG, Brazil. and 4Laboratório Nacional de Luz

Síncrotron, 13083-970, Campinas, SP, Brazil.

Nanodots with magnetic vortices have many potential applications, such as magnetic memories (VRAMs) and spin transfer nano-oscillators (STNOs). Adding a perpendicular anisotropy term to the magnetic energy of the nanodot it becomes possible to tune the vortex core properties. This can be obtained, e.g., in Co nanodots by varying the thickness of the Co layer in a Co/Pt stack. We discuss the spin configuration of circular and elliptical nanodots for different perpendicular anisotropies; we show for nanodisks that micromagnetic simulations and analytical results agree. Increasing the perpendicular anisotropy, the vortex core radii increase, the phase diagrams are modified and new configurations appear; the knowledge of these phase diagrams is relevant for the choice of optimum nanodot dimensions for

applications. MFM measurements on Co/Pt multilayers confirm the trend of the vortex core diameters with varying Co layer thicknesses. Reference: F. Garcia et al. Appl. Phys. Lett. 97, 022501 (2010).

P14. Exploration of spin-wave Bloch modes in hexagonal

lattices with low damping

Fabian Garbs, Benjamin Lenk, and Markus Münzenberg

Physikalisches Institut, Georg-August-Universität Göttingen, Germany

Magnetization dynamics in hexagonal antidot structures are investigated on ultrashort timescales. By analyzing spin waves in micron size structured thin

films of nickel or CoFeB new modes can be observed. In nickel mainly localized spin waves occur due to the inhomogeneities in the internal field around the antidots, while the low damping CoFeB allow spin waves to propagate several hundred micrometers along free paths in the structure (see Figure). Both modes show dependences on the external field alignments. Changing the in-plane angle causes frequency shifts in the localized modes while delocalized modes are forced to propagate along the defined paths of the structure. Strong changes in the spectra were found for directions of high symmetry. By sample rotation about the film normal the observed spin waves reflect the sixfold symmetry of the hexagonal and honeycomb antidot lattices. With an all optical pump-probe experiment the spin waves are detected at the picosecond timescale until 1 ns after excitation. By using the time resolved measurement magneto-optical Kerr effect (TRMOKE) magnetic oscillations

are observed in external fields of up to 150 mT. The sample is 360° rotated in plane for these studies and the field direction can be tilted up to 30° out of plane.


47

P15. Standing spin waves in NiFe/FeMn/NiFe exchange-biased

asymmetrical trilayers

Fernando Pelegrini

1, Valberto P. Nascimento

2, Armando Biondo

2, Edson C.

Passamani2, and Elisa Baggio Saitovitch

3

1Instituto de Física, Universidade Federal de Goiás, Goiânia, Brazil.

2Departamento de Física, Universidade Federal do Espírito Santo, Vitória,

Brazil. 3Centro Brasileiro de Pesquisas Físicas, Rio de Janeiro, Brazil

The Ferromagnetic Resonance (FMR) technique was employed to study at room temperature the magnetic properties of NiFe(30nm)/FeMn(15nm)/NiFe(10nm) asymmetrical trilayers. The samples

studied were produced by DC magnetron sputtering under constant Ar

working pressure of 2, 5 and 10 mTorr, in the presence of a 460 Oe magnetic field used to set the unidirectional anisotropy. The FMR experiments were done using a high sensitivity Bruker ESP-300 spectrometer operating at the microwave frequencies of 9.6 and 33.8 GHz, with swept static field and the usual modulation and phase sensitive detection techniques. At the microwave frequency of 9.6 GHz only the uniform NiFe absorption mode is excited by the microwave field; at the frequency of 33.8 GHz, however, as the magnetic field is swept a low field absorption mode, considered as a spin wave resonance mode, and the uniform NiFe absorption mode are excited by the microwave field. The study of the in-plane angular dependences of the absorption fields reveals for both modes the effect of the unidirectional anisotropy. The dependences of the absorption fields on cosθ, where θ is the field angle with respect to the unidirectional anisotropy axis, give for the sample produced

under working pressure of 2 mTorr, the unidirectional anisotropy fields of 72 and 34 Oe, for the spin wave and uniform absorption modes, respectively. The analysis of the in-plane measurements according to the well known spin wave resonance theory give for the exchange constant of the 30 nm thick NiFe layer in this sample, the value of 1.35 x 10

-6 erg/cm.

[1] V. P. Nascimento, E. Baggio-Saitovitch, F. Pelegrini, L. C. Figueiredo, A. Biondo, and E. C. Passamani, J. Appl. Phys. 99, 08C108 (2006).

[2] W. Stoeklein, S. S. Parkin and J. C. Scott, Phys. Rev. B 38, 6847 (1988).

[3] M. Nisenoff and R. W. Terhune, J. Appl. Phys. 36, 733 (1964).

[4] V. S. Speriosu, S. S. P. Parkin, and C. H. Wilts, IEEE Trans. Magn. 23,

2999 (1987).

P16. Graphene-based spin current waveguides: a theoretical

framework

Filipe S. M. Guimarães

Instituto de Física, Universidade Federal Fluminense, Niterói, RJ, RJ, Brazil.

The issue of magnetic interaction between dopants in carbon-based structures is of growing interest due to its potential applicability in future spintronic devices. Carbon is known as a promising material for spintronic

2nd


48

applications but can only reach its full potential if the interaction between magnetic objects embedded into the carbon environment is fully understood. Two aspects of this magnetic interaction must be considered, depending on whether or not the magnetizations involved are in motion. The so-called dynamic and static magnetic couplings are studied separately and their differences explained. For the dynamic aspect of the magnetic coupling we show how the motion of magnetic moments might be explored so that graphene-based materials may function as low-loss spin-current waveguides. Furthermore, by exploring the electronic properties of graphene, we can envisage this material acting also as a possible spintransistor and as a lens for the spin current.

P17. Spin waves in antidot lattices on suspended membranes

Florian Brandl, Rupert Huber, Sebastian Neusser, Georg Dürr, and Dirk Grundler


Germany

For applications in magnonics [1,2] reliable preparation techniques for magnonic crystals are needed. Direct patterning with chemical etchants and focused ion beam etching might modify the magnetic materials properties due to chemical modification and ion implantation, respectively. To avoid this, self-aligned nanostructuring techniques would be useful. We have developed a new fabrication method for magnetic antidot (AD) lattices based on a photonic crystal consisting of a periodic array of nanoholes etched into a freestanding

Si membrane. The membrane is covered subsequently with thermally evaporated Ni80Fe20. Using all-electrical spin wave spectroscopy [1] we perform measurements on such AD samples with different lattice constants and hole diameters. Applying an external magnetic field B of up to 100 mT in the plane of the AD lattices we find a series of resonant modes which depend characteristically on B. We perform micromagnetic simulations to analyze the AD modes in detail and compare to results obtained on directly patterned Ni80Fe20 antidot lattices [3]. We acknowledge financial support through the German excellence cluster “Nanosystems Initiative Munich” and the European Community‟s Seventh Framework Programme (FP7/2007-2013) under Grant Agreement no. 228673 MAGNONICS.

[1] S. Neusser and D. Grundler, Adv. Mater. 21, 2927 (2009).

[2] V.V. Kruglyak, S.O. Demokritov, and D. Grundler, J. Phys. D: Applied Physics 43, 264001 (2010). [3] S. Neusser et al., Phys. Rev. Lett. 105, 067208 (2010); and references therein.

P18. Spin current injection by spin Seebeck and spin pumping

effects in YIG/Pt structures

Gilvânia L. da Silva, L.H. Vilela-Leão, S. M. Rezende, and A. Azevedo

Departamento de Física, Universidade Federal de Pernambuco, 50670-901,

Recife, PE, Brazil.

We report an investigation of pure spin current injection in Pt stripes deposited

on Yttrium Iron Garnet (YIG) films by using spin pumping (SPE) and spin Seebeck (SSE) effects. Both effects were characterized by measuring the DC voltage created along the Pt stripes by means of the inverse spin Hall effect (ISHE). The samples consist of rectangular YIG films typically with length 5.0

mm, width 1.5 mm and thickness 25 m on which three stripes of Pt were sputter-deposited transversely to the long direction. One Pt stripe is located on the middle and the other two are located close to the ends of the YIG film strip. The Pt stripes have thickness 6 nm and lateral dimensions 1.5 mm and


49

0.15 mm. The DC voltage induced by the ISHE is measured directly with a

nanovoltmenter by two Cu wires attached to the ends of the Pt stripes with silver paint. Spin pumping and spin Seebeck effects are simultaneously activated by exciting the ferromagnetic resonance (FMR) of the YIG film at the same time that a temperature gradient is created along the sample length. By measuring the DC voltage we were able to separate the contributions from SPE and SSE. While the SPE voltage polarity depends on the direction of the applied external field, the SSE voltage depends on the temperature gradient. By varying both the direction of the FMR magnetic field and the temperature gradient we were able to separate accurately both contributions as well as to understand the role played by the spin current polarization generated by SSE and SPE. We also were able to identify as well as quantify the contributions from the different magnetostatic modes excited by FMR to the SPE voltage by solving the magnetostatic Walker equation for a rectangular film.

P19. Spatial profile of both thermal and pumped spin waves in

magnetic nanostructures investigated by micro-focused

Brillouin light scattering

Giovanni Carlotti, Gianluca Gubbiotti, Marco Madami, and Silvia Tacchi

CNISM – Dipartimento di Fisica, Università di Perugia, Italy

The dynamical properties of patterned magnetic sub-micrometric elements have attracted an increasing interest in the last decade because of the observation of new effects induced by the lateral confinement on the spin excitation spectrum, such as the existence of stationary (non-propagating), as

well as localized, magnetic modes. However, no direct experimental evidence of mode localization could be achieved, due to the lack of lateral resolution in conventional BLS measurements. In fact, several thousands of nano-elements are illuminated because of the relatively large laser spot size (about 30-40 μm) and the information obtained is averaged over such a large number of elements. Therefore, the attribution of a determined mode profile to the measured frequency is not possible from the inspection of one single BLS spectrum. These limitations can be overcome using micro-focused BLS, because light can be focused onto a particular portion of a single sub-micrometric object and two-dimensional maps of the mode intensity with lateral resolution of about 250 nm can be performed, thanks to automatic active stabilization and auto-focusing routines which can compensate sample mechanical drift and permit to extend the measurement time to several days. Here we describe the advances in the study of the spatial profile of thermal

spin wave eigenmodes of a single nano-object permitted by the micro-focused Brillouin light scattering technique, recently setup by our group in Perugia. In particular, we focus on the field dependence of both the frequency and the spatial profiles of magnetic modes in elliptical nanorings, both before and after the vortex-to-onion transition. Emphasis is given to the role played by localized soft modes in the reversal mechanism of the magnetization in nanomagnets showing the correlation between soft modes (i.e., modes with a frequency going to zero at the critical field) and magnetic phase transitions. Moreover, we will report on recent results concerning the mapping of spin waves excited in permalloy films and in antidot arrays by the RF field generated by an alternated current injected in a coplanar waveguide. Finally, we will anticipate some preliminary results about the spatial profile of spin-tranfer-torque driven spin waves, excited by a DC current injected into a nanocontact.

This work was supported by CNISM under -BLS Innesco 2006 Project and by the European Community's Seventh Framework Programme (FP7/2007-2013) under Grant Agreement n°228673 (MAGNONICS).

2nd


50

P20. Spin Wave Propagation in Thin Micron-sized Permalloy

Stripes

Hans Bauer, Georg Woltersdorf and Christian Back

Universität Regensburg, 93043 Regensburg, Germany

The wavelength of propagating spin waves has often been determined in thin ferromagnetic films and more recently in structured Permalloy films [1][2]. Thin stripes are of particular interest for micron-sized spin wave devices as they serve as the building blocks for spin wave wave guides in future spin logic devices and spin wave Mach-Zender interferometers. For realization of such devices with only a few micron in size, the knowledge of the damping length of propagating spin waves within the structure is essential.

We used a TR-MOKE setup with 250 nm spatial resolution to study propagating magnetostatic spinwaves in micron-wide Permalloy stripes. As the MOKE signal is proportional to the amplitude of the dynamic magnetization the wavelength and the dampinglength can both be directly determined at the same time. The results are compared to analytical calculations taking the excitation profile into account as well as with micromagnetic simulations. [1] V. E. Demidov et al., Phys. Rev. B 77, 064406 (2008) [2] S. Neusser et al., Phys. Rev. Lett. 105, 067208 (2010)

P21. Tailoring Magnetization Dynamics at Nanoscale

Igor Barsukov, Y. Fu, A. Rubacheva, F. Römer, R. Meckenstock, J. Lindner, and M. Farle

Center for Nanointegration, University Duisburg-Essen, Germany

Controlling spin relaxation is essential for spintronic and spin torque applications. Manipulating spin relaxation allows the adjustment of magnetization reversal speed at microwave frequencies. Moreover, the critical current in spin torque devices can be reduced and tuned. In the experiment it is possible to distinguish between the intrinsic and extrinsic relaxation channels. The latter can be tailored with respect to the intensity and anisotropic behaviour. In particular, methods for inducing elementary relaxation channels of uniaxial symmetry and their impact on the magnetization dynamics are discussed in this presentation.

Fe-based thin films have been studied by means of the ferromagnetic resonance technique, by which the intrinsic and extrinsic relaxation processes can be disentangled. While the former are rather isotropic and can be adjusted via spin-orbit interaction, the latter can be modified in an advanced way. It is shown, how crystalline defects, inhomogeneities of chemical composition, and interface modifications can induce the 2-magnon scattering. Control and systematic manipulation of these parameters allow tailoring the overall spin relaxation in a desired manner with respect to the direction of magnetization and precessional frequency.

”Tailoring Spin Relaxation in Thin Films by Tuning Extrinsic Relaxation Channels”, Barsukov, I.; Meckenstock, R.; Lindner, J.; Moller, M.; Hassel, C.; Posth, O.; Farle, M.; Wende, H.; IEEE Trans. Mag. 46(6),

2252 (2010).

“Tailored magnetic anisotropy in an amorphous trilayer”, Yu Fu, I. Barsukov, H. Raanaei, M. Spasova, J. Lindner, R. Meckenstock, M. Farle, and B. Hjorvarsson, J. Appl. Phys. 109, 113908 (2011).

”Magnetocrystalline anisotropy of Fe-Si alloys on MgO(001)”, Zhang, Y. N. and Cao, J. X. and Barsukov, I. and Lindner, J. and Krumme, B. and Wende, H. and Wu, R. Q., Phys. Rev. B 81, 144418 (2010).

“Two-magnon damping in thin films in case of canted magnetization: Theory versus experiment”, Lindner, J. and Barsukov, I. and Raeder,


51

C. and Hassel, C. and Posth, O. and Meckenstock, R. and Landeros,

P. and Mills, D. L., Phys. Rev. B 80, 224421 (2009).

“Spin dynamics in ferromagnets: Gilbert damping and two-magnon scattering”, Zakeri, Kh. and Lindner, J. and Barsukov, I. and Meckenstock, R. and Farle, M. and von Hörsten, U. and Wende, H. and Keune, W. and Rocker, J. and Kalarickal, S. S. and Lenz, K. and Kuch, W. and Baberschke, K. and Frait, Z., Phys. Rev. B 76, 104416 (2007).

“Low Relaxation Rate in Epitaxial Vanadium-Doped Ultrathin Iron Films”, Scheck, C. and Cheng, L. and Barsukov, I. and Frait, Z. and Bailey, W. E., Phys. Rev. Lett. 98, 117601 (2007).

P22. Static and dynamic properties of magnetic vortices in

small disks

Jeovani Brandão, Naiara Y. Klein, and Luiz C. Sampaio

Centro Brasileiro de Pesquisas Físicas, 22290-180, Rio de Janeiro, RJ, Brazil.

In small disks, in micro-sized scale, the magnetization is aligned in the disk plane and rotates around the center, forming a vortex. It happens for certain diameter and thickness ranges and for magnetic materials with very low magnetocrystalline anisotropy, such as for a alloy FeNi or FeCoSiB. Formation of vortex ground structure in patterned magnetic thin film elements and its behavior in an external magnetic field have been actively studied during the last few years due to its possible applications in high-density magnetic storage devices. We have studied the static and dynamic properties of vortices in microdisks

using magneto-optical Kerr effect (MOKE) and Magnetic Force Microscopy (MFM). The MOKE setup is based in the longitudinal geometry with one detector in differential mode giving a good signal to noise ratio. The MFM measurements were performed in ac mode to detect the magnetic force between the cantilever tip and surface of the disk. We use a rotating magnetic field of variable frequency and amplitude generated by a coplanar waveguide combined with the magneto-optical Kerr effect to measure the resonant frequency of the precession motion vortex. The resonance frequency is determined by measuring the Kerr rotation as a function of the excitation frequency in waveguide. The vortex motion under the action of pulsed magnetic field can reverse the polarity on the center of the disk and generate spin waves. We will show and discuss how the MFM measurements with applied magnetic field can be used to determine the

vortex core displacement in function of magnetic field. Using the images one can detect the vortex chirality (clockwise and counterclockwise) and measure the dependence of the vortex annihilation field with the disk diameter.

P23. All-optical investigation of propagating and standing spin

waves in magnetic micro-waveguides

Katrin Vogt

1,2, Helmut Schultheiss

1,3, Philipp Pirro


1

1Fachbereich Physik and Forschungszentrum OPTIMAS, Technische

Universität Kaiserslautern, D-67663 Kaiserslautern, Germany. 2Graduate

School Materials Science in Mainz, Staudinger Weg 9, D-55128 Mainz, Germany

3current affiliation: Materials Science Division, Argonne National Laboratory,

Argonne, Illinois

The recently developed technique of phase-resolved Brillouin light scattering (BLS) microscopy allows for the unambiguous experimental visualization of the phase profile of propagating as well as standing spin waves on the micrometer scale. With these developments, BLS microscopy is enhanced to analyze spin-wave propagation in micro-structures and to measure the wavelength of irradiated spin waves with a spatial resolution of 200 nm. So far, this was a missing feature of BLS microscopy since the wave vector is not

2nd


52

accessible in the microscopical approach of Brillouin light scattering. The combination of the high sensitivity of BLS microscopy with the novel phase resolution opens the gate to a new class of fundamental experiments like the investigation of spin waves interacting with topological objects such as domain walls. We demonstrate our first results of investigations on spin-wave transport phenomena in soft-magnetic Ni81Fe19 micro-waveguides using phase-resolved BLS microscopy [1]. We carefully investigate the phase accumulation of propagating spin waves in waveguides on the micrometer length scale as a function of the applied magnetic field (see Fig. (a)). The obtained results show an excellent agreement with the theoretically predicted spin-wave dispersion (see Fig. (b)). In addition, we report on the superposition of lateral standing spin waves in a Ni81Fe19 microstripe with the homogeneous excitation driven by the oscillating

magnetic far field of the microwave antenna exciting the spin waves. We demonstrate that this superposition leads to a modification of the amplitude and phase profile of the standing spin waves which is ultimately revealed by an amplification or suppression of the spin-wave antinodes, depending on whether they are in or out of phase with the exciting microwave far field, respectively. These results shed new light on the excitation of standing and propagating spin waves in small magnetic structures. [1] K. Vogt, H. Schultheiss, S. J. Hermsdoerfer, P. Pirro, A. A. Serga, and B. Hillebrands, Appl. Phys. Lett. 95 182508 (2009)

P24. Magnons in Ultrathin Fe films: The Influence of the

Dzyaloshinskii-Moriya Interaction

Kh. Zakeri

1, Y. Zhang

1, J. Prokop

1, T.-H. Chuang

1, W.X. Tang

1,2, and J.

Kirschner1

1 Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle,

Germany. 2 School of Physics, Monash University, Victoria 3800, Australia

We report the experimental results of high wave-vector magnon excitations in ultrathin ferromagnetic Fe films epitaxially grown on W(110), obtained using spin-polarized electron energy loss spectroscopy (SPEELS). The magnon dispersion relation, probed up to the surface Brillouin zone boundary for different thicknesses of Fe layer, will be discussed in detail [1,2]. Furthermore, by presenting the spectra measured in energy loss and gain regions and for different propagation directions, we demonstrate that the magnons propagating along two opposite (but equivalent) directions possess different energies (see Fig. 1). The degeneracy breaking of magnons is attributed to the presence of the Dzyaloshinskii–Moriya interaction in the

system. Starting with the experimental magnon dispersion relation and employing an extended Heisenberg spin Hamiltonian, we will introduce a way to quantitatively obtain the components of the Dzyaloshinskii-Moriya vector [3]. [1] J. Prokop, W. X. Tang, Y. Zhang, I. Tudosa, T. R. F. Peixoto, Kh. Zakeri, and J. Kirschner, Phys. Rev. Lett. 102, 177206 (2009).

[2] Y. Zhang, P. Buczek, L. Sandratskii, W.X. Tang, J. Prokop, I. Tudosa, T.R.F. Peixoto, Kh. Zakeri, and J. Kirschner, Phys. Rev. B 81, 094438 (2010).


53

[3] Kh. Zakeri, Y. Zhang, J. Prokop, T.-H. Chuang, N. Sakr, W. X. Tang, and

J. Kirschner, Phys. Rev. Lett. 104, 137203 (2010).

Fig. 1: Series of asymmetry, SPEEL spectra measured for ΔK|| = ±0.5 Å

-1 on a 2

ML Fe/W(110) at 300 K. The filled symbols are for M|| 101 direction

and the open ones are for M|| ]011[ direction.

The big triangles mark

the peak positions of magnon creations and annihilations, taking place at energy loss and gain, respectively.

-80 -40 0 40 80 120

-40

-20

0

20

40

60

Asy

mm

etr

y (

%)

Energy (meV)

M|| [110]

M|| [110]

Energy lossEnergy gain

I + I

I - I

Asy.=

0.5Å-1

-0.5Å-1

-0.5Å-1

0.5Å-1

P25. Tailoring Spin Dynamics by Magnetic Nanopatterning

Using Ion Irradiation

Kilian Lenz, Michael Körner, Anja Banholzer, Maciej Oskar Liedke, Jochen

Grebing, Jeffrey McCord, and Jürgen Fassbender

Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, P.O. Box 510119, 01314 Dresden, Germany

Various elements like Pd, Cr, Ta, as well as several rare-earth elements can be used to modify the magnetic properties of thin ferromagnetic films. They are incorporated either by co-sputtering or ion implantation and are well known to reduce the Curie temperature, saturation magnetization, anisotropy and damping [1,2]. In combination with lithographic masking this allows for magnetic property patterning at the nanoscale [3]. In thin ferromagnetic films, the magnetization dynamics are governed by intrinsic effects like Gilbert damping and spin-pumping but also by extrinsic effects like two-magnon scattering due to inevitable defect structures. By lithographic nanopatterning or by using ion-eroded, nanoscale periodically modulated substrates (ripples) as templates we are able to artificially create

and thus control those defect structures necessary to induce two-magnon scattering. The damping contributions are disentangled from linewidth measurements by broadband ferromagnetic resonance technique. [1] J. Fassbender and J. McCord, Appl. Phys. Lett. 88, 252501 (2006). [2] J. Fassbender et al., Phys. Rev. B 73, 184410 (2006). [3] J. Fassbender et al., New. J. Phys. 11, 125002 (2009).

P26. Unidirectional anisotropy in the spin pumping voltage in

YIG/Pt bilayers

L. H. Vilela-Leão, C. Salvador, A. Azevedo, and S. M. Rezende

Departamento de Física, Universidade Federal de Pernambuco, 50670-901,

Recife, PE, Brasil.

We report a detailed investigation of the DC voltage (VSP) generated in a Pt layer by magnetostatic modes excited by a microwave field in an adjacent film of yttrium iron garnet (YIG) through the spin pumping effect (SPE). The samples consist of YIG films grown on GGG substrates with thickness of 24

and 28 m having rectangular shape with dimensions of a few mm on which a 6 nm Pt layer was sputter-deposited under an in-plane magnetic field (Hdep) of 200 Oe. The DC voltage generated in the Pt layer by the spin current through

2nd


54

the inverse spin Hall effect (ISHE) was measured directly in a nanovoltmeter connected to two Cu wires attached to the edges of the Pt layer. Field sweep measurements were made to obtain spectra of the microwave absorption and of VSP. The VSP measurements in a direction perpendicular to the in-plane field exhibit peaks corresponding to the microwave absorption spectra for magnetostatic (MS) modes of the YIG film showing an enhanced spin pumping effect for the surface modes.

1 We discovered that the amplitude of

the strong peak in VSP corresponding to one of the MS surface modes exhibits a strong unidirectional anisotropy in the direction of Hdep. If the direction of the external field is reversed, while the shape of the microwave absorption spectrum does not change, the VSP spectrum changes sign and the strong peak becomes twice as large. On the other hand no unidirectional anisotropy is observed in VSP when the electrodes are rotated by 90 degrees and the voltage is measured in a direction perpendicular to Hdep. Since the broadening

of the MS mode lines due to the spin-pumping mechanism of the Pt layer is not affected by the direction of the field we conclude that the unidirectional anisotropy is produced by the mechanism underlying the ISHE of the Pt layer deposited on the magnetized YIG film. This work was supported by Brazilian agencies FINEP, CNPq, CAPES and FACEPE. 1C.W. Sandweg, Y. Kajiwara, K. Ando, E. Saitoh, and B. Hillebrands, Appl.

Phys. Lett. 97, 252504 (2010).

P27. Topological magnetic structures in Mn corrals on Pt(111)

surface

Marcelo Ribeiro

1, Gregório B. CorrêaJr

1, Anders Bergman

2, Lars Nordström

2,

Olle Eriksson2, and Angela Klautau

1

1Faculdade de Física, Universidade Federal do Pará, Belém, PA, Brazil.

2Department of Physics and Astronomy, Uppsala University, Box 516, S-

75120 Uppsala, Sweden.

We study the electronic structure and magnetic properties of Mn corrals adsorbed on a Pt(111) surface in the framework of Density Functional Theory (DFT). The calculations are performed using the first principles realspace linear muffintin orbital method (RSLMTOASA) [1,2] that allows for non collinear magnetic ordering. We find that neighboring Mn atoms present strong antiferromagnetic exchange interactions, leading to collinear magnetic configurations when the geometrical frustration is

avoided, and novel noncollinear ordering for corrals on a frustrated lattice. In particular, we identify a nanoobject presenting very complex stable magnetic configurations, which can be described by topological structures, as skyrmions, in analogy to Z2 vortexlike structures.

Figure 1: Stable magnetic configurations for the Mn corral, composed of six corner-

sharing triangles (AiBiCi) on a Pt(111) surface.

M. S. Ribeiro, G. B. Corrêa Jr., A. Bergman, L. Nordström, O. Eriksson, and A. B. Klautau, Phys. Rev. B 83, 014406 (2011).


55

P28. Dipolar-glass behavior of an amorphous insulating film

containing Fe particles

Martin J. Zuckermann

1 and Norberto Majlis

2

1Department of Physics, Simon Fraser University, Burnaby BC, Canada V5A 1S2.

2Department of Physics, McGill University, Montreal, QC, Canada H3A

2T8

We present results of Monte Carlo simulations of a model of a film of insulating material containing b.c.c. Fe particles which are located at fixed random positions in space and whose magnetization can orientate freely. These dipoles interact only through magnetic dipolar forces. The sign oscillations and the orientation fluctuations of the dipolar interaction in a

disordered system provides the system with frustration necessary to account for the possibility of spin-glass behaviour at low T. We find, for zero applied magnetic field, that at temperatures below a given T = TC the average local spin freezes and the variance of the local field decreases rapidaly. The local time-correlation function for long times (equivalent for this case to the Edwards-Anderson order parameter qEA) saturates to a value close to 1 as T decreases below TC. These properties indicate that such a system of dipoles can exhibit a transition to a glassy state.

P29. Broadband FMR studies in Nanocrystalline films

Marcos P. Alves, J. Gomes Filho, D. E. González Chavez, T. L. Marcondes, and R. L. Sommer

Centro Brasileiro de Pesquisas Físicas, 22290-180, Rio de Janeiro, RJ, Brazil.

The development of microelectronic devices at high frequencies requires soft magnetic materials on nanometer scales. Nanocrystalline films are good candidates for these applications that demand very high signal/noise ratio. Nanocrystalline materials have the structure of an amorphous matrix with a distribution of magnetic nanograins. The best microstructure for applications is reached when FeSi(0.1-0.2) crystals with about 10nm diameter immersed in an amorphous magnetic matrix based on FeSiB. In this case, for bulk materials, permeabilities and coercive fields of about 100000 and 0.01Oe, respectively, are reported [1]. In this work we report the structural, static

magnetic and high frequency permeability measurements of amorphous and partially crystallized FeNbCuSiB films with varying thickness. The X-ray diffraction was used to study the microstructure of the samples, MxH curves were measured with a Vibrating Sample Magnetometer (VSM) and Vectorial Network Analyzer Magnetometry were used for permeability studies in frequencies up to 6 GHz. Broadband permeability measurements shows typical ferromagnetic resonance phenomenon, several resonant modes associated with the magnetic nonuniformities were observed, dispersion relations were obtained and linewidth calculations were made. The results are discussed in terms of anisotropies and microstructure observed in the samples.

P30. Injection locking of tunnel junction oscillators to a

microwave current

M. Quinsat,

1,2,J. F. Sierra,

2 I. Firastrau,

3 V. Tiberkevich,

4 A. Slavin,

4 D.

Gusakova,2 L. D. Buda-Prejbeanu,

2 M. Zarudniev,

1 J.-P. Michel,

1,2 U. Ebels,

2

B. Dieny,2 M.-C. Cyrille,

1 J. A. Katine,

5 D. Mauri,

5 and A. Zeltser

5

1CEA-LETI, MINATEC-Campus, 17 Rue des Martyrs, 38054 Grenoble,

France. 2SPINTEC, UMR CEA/CNRS/UJF–Grenoble 1/Grenoble–INP, INAC,

Grenoble F-38054, France. 3Transilvania University of Brasov, 29 Boulevard

tSSiit

0lim

0

2nd


56

Eroilor, R-500036 Brasov, Romania. 4Department of Physics, Oakland

University, Rochester, Michigan 48309 USA. 5Hitachi Global Storage

Technologies, 3403 Yerba Buena Road, San Jose, California 95135, USA

Spin transfer torque can drive the free layer magnetization of a magneto-resistive device into large angle steady state oscillations. The conversion of these oscillations into a high frequency voltage signal via the magneto-resistance effect is of interest for defining integrated microwave components. However, reducing linewidth and increasing output power remain important issues for such applications. One important route to achieve these goals is to use phase-locked arrays of STNOs

1. Phase locking of two STNOs based on

magnetic nanocontacts via spin wave coupling2,3

and STNOs based on magnetic vortices

4 has been evidenced while mutual phase locking of STNOs

based on magnetic nanopillars and coupled via the generated microwave

current still needs to be experimentally demonstrated. To optimize such mutual phase-locking it is necessary to clearly understand the process of injection-locking of an STNO (having a free running frequency f0) to an external periodic signal of the frequency fe. This effect was demonstrated experimentally in the case of driving by a microwave magnetic field for several rational values of fe/f0.

5 The analytical theory of STNO injection locking

presented in Ref. 5 also predicts that in an in-plane magnetized STNO driven by a microwave current (when the direction of the current spin-polarization is parallel to the axis of symmetry of the STNO trajectory determined by the direction of the bias magnetic field) the locking effect at fe=2nf0 should be substantially more pronounced, than at fe=(2n+1)f0, where n is a natural number. Here we present numerical studies as well as experimental results for injection locking to an external microwave current for an STNO based on a

magnetic tunnel junction whose oscillating and polarizing layers are aligned antiparallel to each other. The STNO devices have the stack composition of IrMn/CoFeB/Ru/CoFeB/MgO/CoFe/CoFeB and a nominal resistance area product of 1 Ωµm2. It is shown that the injection locking takes place only in the vicinity of the point fe=2f0, in agreement with the analytical prediction. A further important result is that noise plays an important role in the injection locking process, and that the frequency-locking does not always mean the exact “phase-locking” of the STNO to an external signal. [1] A. N. Slavin and V. Tiberkevich, IEEE Trans. Magn. 45, 1875 (2009).

[2] S. Kaka et al., Nature (London) 437, 389 (2005).

[3] F. B. Mancoff et al., Nature (London) 437, 393 (2005).

[4] A. Ruotolo et al., Nat. Nanotechnol. 4, 528 (2009).

[5] S. Urazdhin et al., Phys. Rev. Lett. 105, 104101 (2010).

P31. Spin wave resonance in exchange-biased NiFe/IrMn

bilayers

Marcos A. Sousa

1, F. Pelegrini

1, J. Q. Marcatoma

2, W. Alayo

2, and E. Baggio-

Saitovitch2

1Instituto de Física, Universidade Federal de Goiás, Goiânia, Brazil.

2Centro

Brasileiro de Pesquisas Físicas, Rio de Janeiro, Brazil.

The Ferromagnetic Resonance (FMR) technique was used to study the magnetic properties of Si(111)/Ru(7nm)/NiFe(t)/IrMn(6nm)/Ru(5nm) bilayers with thickness t of the NiFe layer in the range 55-120 nm. The samples

studied were produced using the magnetron sputtering technique under constant Ar working pressure of 2 x 10

-3 Torr, in the presence of an applied

field of 400 Oe to set the unidirectional anisotropy. The FMR experiments were done at room temperature using a high sensitivity Bruker ESP-300 spectrometer operating at the microwave frequencies of 9.45 and 34.1 GHz, with swept static field and the usual modulation and phase sensitive detection techniques. As the applied field is swept, the parallel FMR spectra display a low field absorption mode, considered as a spin wave resonance mode, and the uniform NiFe absorption mode. The study of the in-plane angular


57

dependences of the absorption fields at the frequencies of 9.45 and 34.1 GHz

reveals for both modes the effect of the unidirectional anisotropy. The dependences of the in-plane absorption fields on cosθ, where θ is the field angle with respect to the unidirectional anisotropy axis, give for the spin wave and uniform modes for the Si(111)/Ru(7nm)/NiFe(65nm)/IrMn(6nm)/Ru(5nm) sample for example, the unidirectional anisotropy fields of 42 and 20 Oe, respectively. The in-plane measurements and simple spin wave resonance theory give for the NiFe layer of this sample an exchange constant of 1.2 x 10

-

6 erg/cm. This result agrees with the perpendicular out-of-plane FMR

measurement at the microwave frequency of 9.45 GHz.

P32. Electric and magnetic tunability of multiferroic magnonic

crystal

Natalia Grigoryeva, and Boris Kalinikos

Saint Petersburg Electrotechical University, 197376, Saint Petersburg, Russia Ferrite-ferroelectric layered structures, as artificial multiferroics, are intensively investigated during the last ten years [1]. Dual tunability of such heterostructures provides favorable possibilities for development of novel microwave devices whose dispersion characteristics and hybrid-wave nonlinearity can be controlled through changing an applied electric field. Recent success in growing of the ferroelectric films on the surface of hexaferrite material [2] gives a new rise of interest to such structures, since their production creates an opportunity to develop novel signal processing devices for terahertz frequency range [3]. On the other hand, it is well known that microwave spin waves propagating in magnetic periodic structures

(magnonic crystals) exhibit specific properties. In particular, they form the collective eigen-modes and their characteristic spectrum consists of stop and allowed bands [4]. Thus, a combination of the specific spectral properties of the magnonic crystal with dual tunability of multiferroic structures offer a unique model object for microwave applications, as well as for investigation of the wave phenomena in solids. In this work we present the investigation of electric and magnetic tunability of the magnonic crystal based on the multiferroic heterostructure. An analytical theory of the dipole-exchange spin-wave spectrum for such type of magnonic crystal is presented. A relation of the main dispersion characteristics with the parameters of the multiferroic layered structure is determined and analyzed. [1] V. E. Demidov, B. A. Kalinikos, P. Edenhofer, J. Appl. Phys., vol. 91, No.

12, p. 10007 (2002). [2] J. Das, B. A. Kalinikos, A. R. Barman, C. E. Patton, Appl. Phys. Lett., vol. 91, p. 172516, (2007). [3] N. Yu. Grigoryeva, R. A. Sultanov, B. A. Kalinikos, Electronics Letters, vol. 47, No. 1, p. 35 (2011) [4] N. Yu. Grigorieva, B .A. Kalinikos, M. P. Kostylev, A. A. Stashkevich, In Handbook of Artificial Materials (Vol. I), Oxford, UK: Taylor and Francis Group, LLC, 2009.

P33. Direct Observation of First Order Quantum Coherence

and Phase Locking in Magnon Bose-Einstein Condensate

P. Nowik-Boltyk, O. Dzyapko, V. E. Demidov, and S. O. Demokritov

Institute for Applied Physics, University of Muenster, 48149 Muenster,

Germany

Bose-Einstein condensation (BEC) is one of the most fascinating quantum phenomena, as it brings quantum mechanical behavior of bosonic particles on to the macroscopic scale. The latter becomes possible due to emergence of spontaneous coherence between individual bosons comprising condensate, which makes all individual particles to act in a collective manner.

2nd


58

Spontaneous coherence is a crucial point for BEC, determining BEC-based effects such as superconductivity superfluidity and Josephson effect. Here we report on direct experimental observation of coherence in Bose-Einstein condensate of magnons in yttrium-iron garnet (YIG). Discovered by Demokritov [1], condensation of magnons was the first room temperature condensation. Besides, magnon BEC in tangentially magnetized films differs from all other known BEC systems by the fact that condensation occurs at non-zero value of wave vector |kBEC|≠0, which results in degeneracy of the quantum state of the condensate (due to symmetry reasons magnons condensate at two points of phase space corresponding to ±|kBEC|). In our experiments we create magnon condensate by means of continuous parametric pumping. Continuous pumping allows for constant initial phase of the condensate during the whole measurements. Condensate properties are investigated by space and time resolved micro-focus Brillouin light scattering

technique [2]. In the experiment we directly observe interference pattern, which results from the interference between two components of magnon condensate from different points of phase space. Stationary interference pattern appears as a result of phase locking between two condensates, which keeps difference between phases of individual condensates constant during the whole measurements. The phase locking arises as a result of nonlinear interaction between magnons from different condensates. This conclusion is corroborated by observation of increase of phase locking rate with pumping power.

[1] S. O. Demokritov, V. E. Demidov, O. Dzyapko, G. A. Melkov, A. A. Serga, B. Hillebrands, and A. N. Slavin, Nature 443, 430 (2006).

[2] V. E. Demidov, S. O. Demokritov, B. Hillebrands, M. Laufenberg, and P. P. Freitas, Appl. Phys. Lett. 85, 2866 (2004).

P34. Tailoring magnetic relaxation in thin films with different

defects features

P. Landeros

1, R. E. Arias

2, and D. L. Mills

3

1Departamento de Física, Universidad Técnica Federico Santa María, Av.

España 1680, Valparaíso, Chile. 2Departamento de Física, FCFM,

Universidad de Chile, Casilla 487-3, 8370415 Santiago, Chile. 3Department of

Physics and Astronomy, University of California, Irvine, California 92697, USA.

We investigate the role of different defects structures on the magnetic

relaxation of ultrathin films. It is well know that defects on magnetic surfaces modify the damping of the spin motions through the coupling of spin waves modes, a phenomenon that may be exploited to manipulate the time response of a nanomagnet. We find that the angular dependence of the linewidth of the ferromagnetic resonance lineshape can be controlled in an experiment through different defects features, which can be either of geometrical nature or in the atomic structure of the film. We consider arrays of random defects, periodic arrays of stripe defects as well as local regions with different magnetic anisotropy.

P35. Dymanic magnetization studies in NiFe/IrMn/Ta exchange

biased

R. Dutra1, D. E. Gonzàlez-Chávez

1, A. M. H. de Andrade

2, and R. L.

Sommer1

1Centro Brasileiro de Pesquisas Físicas.

2Universidade Federal do Rio

Grande do Sul The dynamic properties of magnetic materials have been extensively studied for the last over half a century due to their applications in many high frequency devices. For such kinds of applications, magnetic materials should possess a


59

high static permeability and high ferromagnetic resonance frequency.

Exchange biased thin films employing the exchange coupling between a ferromagnet and an antiferromagnet have been proven to be a good candidate for microwave thin films, its effect can be used to extend the FMR significantly. In this work we report high frequency permeability measurements of multilayered samples based on Permalloy and IrMn plus a Ta spacer, exhibiting the Exchange Bias phenomenon. The samples with structure [Ni81Fe19(tpy)/Ir20Mn80(15nm)/Ta(3nm)]x30 with tpy =10nm, 15nm and 20nm were produced by magnetron sputtering onto (100) silicon substrates under a 1kOe magnetic field. The structural properties of the samples were characterized by x-ray diffraction (low angle and high angle). The magnetic properties were measured by VSM. Broad band high frequency permeability measurements were made with a vector network analyzer (Rohde&Schwarz ZVA24 VNA) combined with a microstrip inductive waveguide in the frequency

range 500 MHz to 6.5 GHz. We observed the dependence of the resonance frequency on the Permalloy layer thickness, the dispersion relation curves and linewidth.

P36. Tuning misalignment of ferromagnetic and

antiferromagnetic easy axes in exchange biased bilayers

R. L. Rodríguez-Suárez

1, L. H. Vilela- Leão

2, T. Bueno

2, J. B. S. Mendes

2, P.

Landeros3 ,S. M. Rezende

2, and A. Azevedo

2

1Facultad de Física, Pontificia Universidad Católica de Chile, Casilla 306,

Santiago, Chile. 2Departamento de Física, Universidade Federal de

Pernambuco, Recife, PE 50670-901, Brasil. 3Departamento de Física,

Universidad Técnica Federico Santa Maria, Avenida España 1680, 2390123 Valparaíso, Chile.

In this work, the angular dependence of the ferromagnetic resonance (FMR) field and linewidth of exchange biased Ni81Fe19/ Ir20Mn80 (ferromagnetic/ antiferromagnetic) bilayers prepared by oblique sputtering with a noncollinear uniaxial and unidirectional anisotropy configuration are studied. The samples were grown under the influence of an in situ magnetic field, non-colliniar with the easy axis direction of the ferromagnetic film. We demonstrated that the exchange coupling leads to misalignments between the applied field during growth, the ferromagnetic easy axis and the antiferromagnetic easy axis directions. From the angular dependence of the resonance field and the linewidth we were able to extract the anisotropies fields and the misalignments angles.

P37. Josephson Effect in Bose-Einstein Condensate of

Magnons at Room Temperature

Roberto Troncoso and Alvaro S. Nuñez

Universidad de Chile, Av. Blanco Encalada 2008, Santiago, Chile.

Once the population of magnons, created through a time dependent magnetic field in a YIG magnetic thin film, surpasses a critical level, the system becomes a macroscopic condensate. Despite decay processes, ongoing during the condensate formation, the system manifests spontaneous quantum coherence with a pseudo-spin degree of freedom originated from the presence of two, well separated, valleys in momentum. A real space

description of the condensed state is provided revealing the condensate state as a Spin Density Wave. One of the most striking phenomena in the nature of macroscopic quantum systems, such as the Magnon BEC, is the emergence of a macroscopic phase as consequence of a spontaneous symmetry broken, where the state is characterized both the density and coherent phase. The quantum collective dynamics between coherent many-body systems spatially separated is described by macroscopic observables as the population imbalance and relative phase, and the interference phenomena of such states is referred as the Josephson effect. The realization of the Magnon Bose-

2nd


60

Einstein Condensate in a YIG ferromagnetic crystal naturally suggests the idea of separate spatially the cloud condensate in two by means of a current that goes through a conductor placed transversely to the YIG sample and and changes locally the magnetization upon the YIG[1]. Within this settings we unveil the macroscopic quantum coherence character studying the Josephson Effect[2]. The magnon BEC manifest Josephson's Oscillations which internal oscillations (oscillation between valley) are coupled with the external oscillations (oscillations between the two separate clouds) that reveals the asymmetric magnon current between states spatially separated. The amplitude and frequency of the population imbalance and the relative phase oscillations are determined as a function of the in-plane magnetic field applied upon the YIG sample, Ho, and the local inhomogeneity in the magnetization due to the dc current applied, Hin, and proven to be experimentally relevant since the frecuency of Josephson's Oscillations are lower respect to the

resolution frequency of the BLS technique, ωJ < ωBLS. We predict the dynamical behavior of the Spin Density Wave whose behavior is characterized by Josephson's Oscillations above mentioned and we show the existence of Macroscopic Quantum Self-Trapping of magnons for a certain region within the parameter space (Ho,Hin) and initial conditions. [1] S. O. Demokritov, A. A. Serga, A. Andre, V. E. Demidov, M. P. Kostylev, A. N. Slavin and B. Hillebrands, Phys. Rev. Lett. 93, 047201 (2004). [2] R. E. Troncoso and Alvaro S. Nuñez in preparation.

P38. Magnetostatic band gaps in geometrically modulated thin

films

Claudio Jarufe, and Rodrigo Arias

Universidad de Chile, Av. Blanco Encalada 2008, Santiago, Chile.

We present a theory of the nature of spin wave modes in thin films whose surfaces are geometrically modified along one dimension: there is a uniform magnetic field applied on the plane of the film that magnetizes it in that direction, and the geometric perturbation profile is perpendicular to the previous direction. We confine our analysis to the magnetostatic limit, and we do find the frequency dispersion relation of spin wave modes that propagate with a wave vector perpendicular to the direction of translational invariance, or the applied magnetic field direction. We focus our attention into periodic geometric modulations of the surfaces of the films. Thus, the dispersion

relations can be referred to a first Brillouin zone, and we do find band gaps at the edge of this zone. The underlying theory for calculating these modes was presented previously, and it involves solving an integral equation along the edge of the sample for the magnetostatic potentials. In particular we do study a geometrical modulation of the surface of periodic sinusoidal shape, that is amenable to analysis in the small perturbation limit. Furthermore, there is a simple analytic way to estimate the magnitude of the first band gaps. Thus, one could in principle engineer the frequency band gaps by appropriately choosing the geometric modulation of the surface and its parameters. A more general geometry can be studied by use of a Fourier analysis of the shape of the geometric perturbation of the surface.

P39. Spin-wave propagation through a reprogrammable one-

dimensional magnonic crystal

Rupert Huber, Sebastian Neusser, Georg Dürr, Thomas Schwarze, and Dirk

Grundler

Lehrstuhl für Physik funktionaler Schichtsysteme, Technische Universitaet Muenchen, Physik Department, James-Franck-Str. 1, D-85747 Garching,

Germany


61

Artificial crystals (ACs) and metamaterials are of great interest as they allow

one to tailor precisely the wave dispersion and wave properties via geometrical parameters. ACs have been explored in different areas of physics, such as photonics, phononics, plasmonics, and recently also magnonics. For spin waves a periodically modulated ferromagnetic material leads to allowed bands and forbidden frequency gaps in certain propagation directions. For instance, a one-dimensional magnonic crystal is obtained by a closely packed array of interacting magnetic wires. In parallel magnetic orientation detailed measurements via Brillouin light scattering have evidenced an artificial band structure induced by the periodic nanopatterning [1,2]. We present all-electrical spin wave (SW) spectroscopy on an array of interacting magnetic nanowires as depicted in Fig. 1.

Fig. 1: (left) SEM image of permalloy nanowires (brown). Every second wire is connected to a nucleation pad to narrow the switching field distribution. (right) The air gap, i.e., the edge-to-edge separation, is about 45 nm Using two collinear coplanar waveguides [3] we explore SW propagation perpendicular to the wires, i.e., across the air gaps. We control precisely the magnetic configuration by using a nucleation pad. This is connected to every second wire in order to be able to control the switching of these wires independently to neighboring wires. We compare SW propagation at the same frequency in the two different magnetic states where neighboring wires are magnetized in either the parallel or antiparallel configuration [4]. Characteristic properties such as the SW propagation velocities are presented for this magnonic crystal exhibiting a reprogrammable band structure. The research leading to these results has received funding from the European

Community‟s Seventh Framework Programme (FP7/2007-2013) under Grant Agreement no. 228673 (MAGNONICS) and the German Excellence Cluster Nanosystems Initiative Munich‟. [1] G. Gubbiotti et al., Appl. Phys. Lett. 90, 092503 (2007).

[2] C.C. Wang et. al., Appl. Phys. Lett. 94, 083112 (2009).

[3] S. Neusser et al., Phys. Rev. Lett. 105, 067208 (2010).

[4] J. Topp et al., Phys. Rev. Lett. 104, 207205 (2010).

P40. Energy transfer between vortex-state magnetic disks by

stimulated vortex gyration

Hyunsung Jung,

1 Ki-Suk Lee,

1 Dae-Eun Jeong,

1 Youn-Seok Choi,

1 Young-

Sang Yu,1 Dong-Soo Han,

1 Andreas Vogel,

2 Lars Bocklage,

2 Guido Meier,

2

Mi-Young Im,3 Peter Fisher,

3 and Sang-Koog Kim

1

1National Creative Research Initiative Center for Spin Dynamics and Spin-Wave Devices, Nanospinics Laboratory, Department of Materials Science and Engineering, College of Engineering, Seoul National University, Seoul 151-744, Republic of Korea.

2Institut für Angewandte Physik und Zentrum

für Mikrostrukturforschung,Universität Hamburg, Hamburg, Germany

2nd


62

3Center for X-ray Optics, Lawrence Berkeley National Laboratory, Berkeley,

CA, California 94720, USA

A wide variety of coupled harmonic oscillators exist in nature. Coupling between different oscillators allows for the possibility of mutual energy transfer between them and the information-signal propagation. Low-energy input signals and their transport with low-energy dissipation are the key technical factors in the design of information processing devices. Here, utilizing the concept of coupled oscillators, we experimentally demonstrated a robust new mechanism for energy transfer between spatially separated dipolar-coupled magnetic disks - stimulated vortex gyration[1,2]. Direct experimental evidence was obtained by time-resolved soft X-ray microscopy. The rate of energy transfer from one disk to the other was deduced from the two normal modes‟ frequency splitting caused by dipolar interaction. This mechanism provides the

advantages of tunable energy transfer rate, low-power input signal, and low-energy dissipation for magnetic elements with negligible damping. Coupled vortex-state disks are promising candidates for information-signal processing devices that operate above room temperature. This work was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (No. 20110000441). [1] H. Jung et al., Appl. Phys. Lett. 97, 222502 (2010).

[2] H. Jung et al., arXiv:1011.6399v1.

P41. Vortex gyratons in magnonic cystals of dipolar coupled

magnetic nanodisks

Dong-Soo Han, Dae-Eun Jeong, and Sang-Koog Kim

National Creative Research Initiative Center for Spin Dynamics & Spin-Wave Devices, Nanospinics Laboratory, Seoul National University, Seoul 151-744,

Republic of Korea

A robust mechanism for energy transfer between spatially separated magnetic disks, based on stimulated vortex gyrations, has been demonstrated both theoretically (and by micromagnetic simulations) and experimentally [1-4]. Such a mechanism produces a new type of signal transfer/propagation between magnetic dots of micrometer size (or less), and does so advantageously through low-energy dissipation and low-power signal input. Here, we report on collective vortex-gyration modes in magnonic crystals,

specifically, one-dimensional (1D) arrays. We analytically constructed band diagrams and compared them with the micromagnetic simulation results for two different arrays of 25 disks. All of the disks were of equal 213 nm diameter and 20 nm thickness, with 15 nm edge-to-edge separations among them; in one array the disks were all of the same material, NiMnSb, while in the other array, the composition alternated between Permalloy and NiMnSb. We calculated the dispersion curves for four different polarization (p) / chirality (c) combinations, as denoted by [pi,ci] = [1,1] , [1,(-1)

i+1] , [(-1)

i+1,1] and [(-1)

i+1, (-

1)i+1

], where i = 1, 2, 3, …, 25. For the single-material array, only one branch, analogous to the optical or acoustic band of phonon frequency, was found, but for the two-alternating-materials array, two different branches were observed. In addition, we found that the shape and width of the bands vary with picipi+1ci+1

and pipi+1, respectively. Also, we analytically derived the group velocity of gyration propagation (which is expressed in terms of the eigenfrequency of an

isolated single disk, the interdistance between neighbouring disks, and the vortex configurations. The above results provide for the possibility that vortex-gyration-based magnonic crystals can be implemented in future information-signal transmission and processing devices, offering the advantages of low energy dissipation, low-power signal input, and fast information propagation. This work was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (No. 20110000441)


63

[1] J. Shibat et al., Phys. Rev. B 67, 224404 (2003).

[2] J. Shibat and Y. Otani, Phys. Rev. B 70, 012404 (2004)

[3] S. Barman et al., IEEE Trans. Mag. 46, 1342 (2010)

[4] H. Jung et al., Appl. Phys. Lett. 97, 222502 (2010); H. Jung et al.,

arXiv:1011.6399v1, A. Vogel et al. Phys. Rev. Lett. 106, 137201 (2011);S.

Sugimoto et al. Phys. Rev. Lett. (in press).

2nd


64

Index

Ahmad, E., 26 Akerman, J., 34 Albuquerque, E.L., 42 Alves, M.J.P., 55 Alayo, W., 56 Ando, K., 32 Arias, R.E., 58, 60 Aschenbach, K., 35 Au,Y.-Y., 26 Auffret, S., 37 Azevedo, A., 31, 48, 53, 59

Back, C., 50 Bader, S.D., 23 Baggio-Saitovitch, E., 47, 56 Bailey, E., 37 Banholzer, A., 53 Barbosa, A., 46 Barsukov, I., 50 Bauer, H., 50 Bergman, A., 54 Biondo, A., 47 Bocklage, L., 61 Bonetti, S., 34 Boone, C., 31

Bortolotti, P., 32 Brandão, J., 51 Brandl, F., 45, 48 Buda-Prejbeanu, L.D., 33, 55 Bueno, T., 59 Burrowes, C., 27 Camley, R.E., 29 Carlotti, G., 26, 34, 49 Celinski, Z., 29 Cerqueira, C.F., 43 Cheng, X., 31 Choi, S., 61 Chouiki, M., 43

Chuang, T.-H., 52 Chumak, A.V., 19, 20, 36, 39 Consolo, G., 34 Correa, M.A., 45 Correa-Jr., G.B., 54 Costa, A.T., 17 Costa, C.H.O., 42 Cros, V., 32 Cyrille, M.-C., 33, 55 Davison,T., 26 Da Silva, G.L., 48 De Andrade, A.M.H., 45, 58

De Loubens, G., 17, 32 Demidov, V.E., 34, 57 Demokritov, S.O., 34, 57 Dieny, B., 33, 55 Drozdovskii, A., 40 Dzyapko, O., 57 Duerr, G., 45 Dürr, G., 48, 60 Dussaux, A., 32


65

Dutra, R., 58

Dvornik, M., 26 Ebels, U., 33, 37, 55 Eriksson, O., 54 Farrel, R.A., 43 Farle, M., 50 Fassbender, J., 53 Fert, A., 32 Fetisov, Y. K., 30 Filimonov, Y. A., 20 Firastrau, I., 55 Fisher, P., 61

Francome, A., 43 Fu, Y., 50 Fukushima, A., 32 Garbs, F., 24, 41, 46 Gangmei, P., 18 Garcia, F., 46 Girt, E., 27 Gonçalves, A.M., 38 Grebing, J., 53 Gregg, J.F., 39 Ghosh, A., 37 Gomes-Filho, J., 41, 55 González-Cháves, D.E., 41, 45, 55, 58

Grigoryeva, N., 29, 57 Grollier, J., 18, 32 Grundler, D., 25, 45, 48, 60 Gubbiotti, G., 26, 34, 49 Guimarães, A.P., 46 Guimarães, F.S.M., 47 Gusakova, D., 33, 55 Guslienko, K., 19 Han, D.-S., 61, 62 Harward, I., 29 Heinrich, B., 27 Hicken, R.J., 18 Hillebrands, B., 19, 20, 36, 39, 51

Holmes, J.D., 43 Huber, R., 45, 48, 60 Im, M.-Y., 61 Jarufe, C., 60 Jeong, D.-E., 61, 62 Jung, H., 61 Jungfleisch, M.B., 36 Kajiwara, Y., 36 Kalinikos, B., 29, 38, 40, 57 Kardasz, B., 39

Karenowska, A.D., 39 Katine, J.A., 33, 55 Keatley, P.S., 18 Kehagias, N., 43 Khivintsev, Y.V., 20, 29 Khvalkovskiy, A., 32 Kim, D.-H., 23 Kim, S.-K., 61, 62 Kirilyuk, A., 22

2nd


66

Kirschner, J., 22, 52 Klautau, A., 54 Klein, N.Y., 38, 51 Klein, O., 17, 32 Koblyanskiy, Y., 19 Kondrashov, A., 29 Körner, M., 53 Krivorotov, I., 31 Kruglyak, V.V., 26 Kuanr, B., 29 Kuchko, A., 26 Landeros, P., 46, 58, 59 Lee, Ki-Suk, 61

Lenk, B., 24, 41, 46 Lenz, K., 53 Lesniak, M.S., 23 Liedke, M.O., 53 Lindner, J.,50 Locatelli, N., 32 Lounis, S., 17 Madami, M., 26, 34, 49 Maekawa, S., 16 Majlis, N., 55 Marcatoma, J.Q., 56 Marcondes, T.L., 45, 55 Martins, M., 46

Matsumoto, R., 28 Mauri, D., 55 McCord, J., 53 McMichael, R.D., 35 Meckenstock, R., 50 Meier, G., 61 Melkov, G.A., 19, 20 Mendes, J.B.S., 59 Mikhaylovskiy, R., 26 Mills, D.L., 17, 58 Michel, J.-P., 55 Monteblanco, E., 33 Montoya, E., 27

Morris, M.A., 43 Muduli, P., 34 Müenzenberg, M., 24, 41, 46 Muniz, R.B., 17 Murakami, S., 28 Naletov, V., 17, 32 Nascimento, V.P., 47 Neusser, S., 45, 48, 60 Nie, Y., 29 Nikitin, A., 29 Nikitov, S., 20 Nordström, L., 54 Novais, E., 46

Novosad, V., 19, 23 Nowik-Boltyk, P., 57 Nuñez, A.S., 59 Obry, B., 20 Padrón-Hernández, E., 31, 59 Passamani, E.C., 47 Pavlov, E., 20


67

Pelegrini, F., 47, 56

Pirro, P., 51 Pogoryelov, Y., 34 Prokop, J., 52 Quinsat, M., 33, 55 Rajh, T., 23 Reboud, V., 43 Rezende, S.M., 31, 48, 53, 59 Ribeiro, M., 54 Rodríguez-Suárez, R.L., 59 Römer, F., 50 Rozhkova, E.A., 23

Rubacheva, A., 50 Saitoh, E., 36 Salvador, C., 53 Sakharov, V., 20 Sampaio, L.C., 38, 43, 51 Sandweg, C.W., 20, 36 Schoeftner, R., 43 Schultheiss, H., 51 Schwarze, T., 45, 60 Serga, A.A., 20, 36, 39 Sierra, J.F., 33, 55 Silva, B.G., 41 Simao, C., 43

Slavin, A., 19, 20, 21, 33, 39, 55 Sommer, R.L., 41, 45, 55, 58 Song, Y.-Y, 27 Sousa, M.A., 56 Sun, Y., 21, 27 Tacchi, S., 26, 49 Tang, W.X., 52 Tiberkevich, V.S., 20, 21, 33, 39 Tkashenko, V., 26 Torres, C.S., 43 Troncoso, R., 59 Ulasov, I., 23

Ulrichs, H., 24, 41 Ulysse, C., 18 Urazhdin, S., 34 Ustinov, A., 29, 38, 40 Vasconcelos, M.S., 42 Vasyuchka, V., 20 Vilela-Leão, L.H., 48, 53, 59 Vogel, A., 61 Vogt, K., 51 Vysotskii, S., 20 Wang, Z., 21

Woltersdorf, G., 50 Wu, M., 21, 27 Yu, Y.-S., 61 Yuasa, S., 32 Zagorodnii, V.V., 29 Zakeri, K., 52 Zarudniev, M., 55

2nd


68

Zeltser, A., 33, 55 Zhang, Y., 52 Zhu, J., 31 Zhu, M., 35 Zelsmann, M., 43 Zuckermann, M.J., 55

2ndinternational workshop on magnonics

Documents