Institute of Physics Polish Academy of Sciences Warsaw, Poland

Division of Physics of Magnetism: ON – 3 http://www.ifpan.edu.pl/index_en.php

Group of Magnetic Heterostructures

Scientific profile: Physics of magnetism of metallic magnetic ultrathin films, multilayers and nanostructures (dots, wires, magnonic crystals)

Andrzej Wawro wawro@ifpan.edu.pl http://info.ifpan.edu.pl/~wawro/

1. Short introduction to magnetic patterning 2. Presentation of MBE for metallic structures 3. Brief review of scientific results > dots > magnonic crystals > coupled layers 4. Summary: possible applications

Outline

Reasons for nanomagnetic system investigations

> fundamental investigations of magnetism in nanoscale: - magnetic anisotropy due to impact of the interface and edge atoms - modifications of magnetic moments of atoms (magnetovolume effect) - Curie temperature - electron polarisation - spin wave propagation - interlayer coupling - electron spin scattering > layered coupled systems: spin valves, GMR > patterned media for magnetic data storage (suppression of superparamagnetism,

increase of density storage, multilevel storage) > sources of local magnetic fields for spintronic systems > magnetic quantum cellular automata for logic operations (MQCA) > magnonic crystals: a new type of metamaterial > sensors e.g. in biology: filters in cell cytometry and hyperthermia therapy

Riber Prevac

MBE systems

Prevac MBE system components:

- growth chamber - MOKE chamber - analysis chamber - ion gun chamber - SPM chamber - UHV: 1E-11 Torr

Prevac system

> 12 pockets (in two electron guns) > 8 effusion cells > available materials: Ni, Co, Fe, Cr, W, Mo, Nb, Ta, V, Pt, Au, Ag, Cu > standard deposition rates: < 0.1 nm/s > RHEED (reflection high electron energy diffraction): crystalline structure > growth of single layers, multilayers, alloys and nanostructures > linear shutter : wedge- and step-like layers, double-wedge systems > sample holders: molyblocks 3” in diameter, temperature up to 1400 °C > standard substrates: 10 x 10 mm

Growth chamber

> measuring configurations: PMOKE (polar; out-of-plane component) LMOKE (longitudinal; in-plane component; angular dependence) > scan over the sample surface > map of remnant magnetization (at H=0) > magnetic fields up to 3.8 kOe MOKE – magnetooptical Kerr effect

Co

MOKE magnetometry chamber

> structural modifications of magnetic systems (interfaces and volume alloying) > noble gases: He, Ar (currently), Ne, Xe > energy range: up to 25 keV > fluences: 1e12 – 1e16 cm-2

> linear shutter: step- or wedge-like profiles of the dose > etching

Ion gun chamber

> low energy electron diffraction (LEED): crystalline structure > Auger electron spectroscopy (AES): chemical composition; diffusional processes > direct heating stage for e.g. semiconducting substrate preparation > e-gun heating stage for sample heating up to 2000 °C

Analysis chamber

Omicron VT SPM XA Series 50 – 500 K scanning probe microscopy (SPM) modes:

> atomic force microscopy (AFM): topography; all materials > magnetic force microscopy (MFM): magnetic domain structure > scanning tunnelling microscopy and spectroscopy (STM/STS): topography and local

electronic structure, only conducting materials

SPM chamber

Co M

easy plane easy axis

M

Magnetization reorientation in thin films

Etot(θ) = -MSH(θ) + K1effsin2(θ) + K2sin4(θ) K1eff(d) = -2πMS

2 + KV + KSB/d + KSO/d

Model of uniaxial anisotropy

d

reorientation phase transition (RPT)

Components of magnetic anisotropy: > magnetocrystalline > magnetoelastic > surface > shape (dipolar)

supe

rpar

amag

netic

Double wedge structures

M. Kisielewski et al., PRL 89 (2002) 087203

Mo

Au

Co

Co

Idea of the magnetic dots induced by a patterned substrate

A. Wawro et al., PRB 83, 092405 (2011)

Magnetic states of dots upon demagnetization

scan size 6 µm

tip: MESP-LM

dCo = 13.5 Å

dots magnetized „up” dots magnetized „down”

dots demagnetized in ac magnetic field with decreasing amplitude

E. Sieczkowska et al., IEEE Trans. Magn. 47, 2632 (2011)

5 mm

10 m

m

(III)

(II)

(I)

Magnetic filtering

(III)

(II)

(I)

scan size: 20 µm

A. Maziewski et al., Phys. Rev., B85 (2012) 054427

Structural modification of Pt/Co/Pt with Ga+ ion beam

Co

13

14

15

16 lo

g F

1D magnonic crystals

PMOKE magnetization reversal

MFM

0 kOe

0.24 kOe

0.52 kOe

TRIDYN simulations

J. Kisielewski et al. J. Appl. Phys. 115, 053906 (2014)

Structural modification of Pt/Co/Pt with laser beam

Interlayer magnetic coupling in Mo/Co bilayers

Summary: towards applications …

Wedged magnetic layers: - cancer cell (containing magnetic nanoparticles) filtering by domain wall movement

for hyperthermia therapy Magnetic dots: - elements of patterned media with perpendicular storage - multilevel magnetic storage (dot – matrix composite) - filter in cell cytometry Patterned structures by ion and laser beams: - magnonic crystals: a new type of metamaterials with band structure that can be

reprogrammed during operation Coupled magnetic layers: - GMR and spin valve effect - spatially patterned coupling: switchable magnonic crystals … and probably many other applications….

Prof. L.T. Baczewski Prof. A. Wawro Dr. L. Gładczuk Dr. A. Petruczik E. Milińska A. Marynowska K. Lasek P. Misiuna M. Jakubowski P. Aleszkiewicz

IPPAS (IFPAN) group and cooperation

Dr. J. Kanak

Prof. A. Maziewski Dr. Z. Kurant Dr. P. Mazalski Dr. I. Sveklo Dr. J. Kisielewski Dr. M. Tekielak

Dr. A. Rogalev Dr. K. Ollefs

Dr. J. von Borany Dr. K. Potzger Dr. R. Boettger

Prof. J. Szade Dr. K. Balin

Dr. A. Bartnik

Prof. Th. Rasing Dr. A. Kirilyuk Dr. A. Kimel