AD-A23 1 764 Final Report

For

ADVANCED STUDY INSTITUTE ON THE SCIENCE & TECHNOLOGY

OF

NANOSTRUCTURED MAGNETIC MATERIALS

Crete, GreeceJune 25, 1990 to July 6, 1990

DTIC- , Submitted to:MARO 6 1 9 :

O6 9 Dr. Larry R. Cooper

Office of Naval Research800 North Quincy Street

Arlington, VA 22217-5000

Grant No.: N00014-90-J-1756

Grant No.: N00014-90-G-0756

R & T PROJECT: 414q OZZ-001

" .Submitted by:

Prof. George C. HadjipanayisUniversity of Delaware

Department of Physics and AstronomyNewark, DE 19716-2570

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Dr. George C. Hadjipanayis (If applicable) Office of Naval Research

Universitv of Delaware. I6c. ADDRESS (City, State, and ZIP Code) 7b. ADDRESS (City, State, and ZIP Code)

Department of Physics & Astronomy Code 1513: ETF

223 Sharp Laboratory 800 N. Quincy Street

Newark. DE 19716 Arlington, VA 22217-5000

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16. SUPPLEMENTARY NOTATION

17. COSATI CODES 18. SUBJECT TERMS (Continue on reverse if necessary and identify by block number)

FIELD GROUP SUB-GROUP , >-Thin Film, Technology & Applications, Magnetics,

Superconductivity, Physics, Solid State .&-

19. ABSTRACT (Continue on reverse if necessary and identify by block number)

The Institute reviewed the remarkable progress made in magnetic materials over the last. few

years and addressed the current state-of-the-art research and its impact on technological appli-

cations. The subject matter fell into a number of broad areas including thin films, multilayers,

disordered systems, ultrafine particles, intermetallic compounds, permanent magnets and magnetic

imaging techniques.

The development of new techniques for materials preparation has made a dramatic impact in

the area of epitaxial growth of magnetic films. Several presentations have shown that this process

can be controlled on the scale of atomic layers permitting the growth of artificial structures such as

artificial superlattices with nearly atomic resolution. Epitaxial growth has also permitted the sta-

bilization of metastable phases in thin films which often possess a strong perpendicular anisotropy,

20. DISTRIBUTION/AVAILABILITY OF ABSTRACT 21. ABSTRACT SECURITY CLASSIFICATION

M UNCLASSIFIED1UNLIMITED [0 SAME AS RPT. r_- DTIC USERS Unclas if[ed

22a, NAME OF RESPONSIBLE INDIVIDUAL N66002 22b. TELEPHONE (Include Area Code) 22c OFFICE SYMBOLDaniel Fesko-Office of Naval Research resetative

DO Form 1473, JUN 86 Previous editions are obsolete. SECURITY CLASSIFICATION OF THIS PAGE

which may prove useful for technological applications. In magnetic multilayers and superlatticesthe complex coupling between different magnetic layers was discussed both experimentally and the-oretically. Magnetic surfaces and interfaces show large magnetic anisotropy (surface anisotropy),coercivity, magnetoresistance, galvanomagnetic and magnetooptic effects that can lead to futurestorage technologies. Several contributions discussed the physics of ultrafine particles and grandu-lar solids with interesting and unique properties from superparamagnetism to strong magnetichysteresis. The magnetic properties of rare-earth intermetallic compounds with potential applica-tions in permanent magnets have been discussed including the crystal field effects and the originof magnetic anisotropy. The magnetic hysteresis behavior of fine particles, permanent magnets,melt-spun ribbons and mechanically alloyed magnets have been discussed.

Finally the applications of magnetic materials in magnetic recording, magneto-optic recordingand permanent magnets have been discussed with more emphasis given to the improvement ofmaterial properties for these applications.

I

CHAPTERS

1. Thin Films, Surfaces and Interfaces

II. Multilayers

11). Domain Walls, Magnetic Domains and Techniques for Their Observation

IV. Magnetic Anisotropy and Random Magnets

V. Magnetic Semiconductors and Internietallic Compounds

VI. Fine Particles

VII. Magnetic Hysteresis and Permanent Magnets

I - VBYII>

ED.QC.

Statement "A" per Dr. Larry Cooper.ONR/Code 1114SS.

VHG 3/5/91

- -June 25 - July 6, 1990Heraklion (Aghia Pelayla) Crete, Greece

Dr. George C. HadjipanayisDept. of Physics & AstronomyUniversity of Delaware, Newark, DE 19716

The Institute reviewed the remarkable progress made in magnetic materials over thelast few years and addressed the current state-of-the-art research and its impact ontechnological applications. The subject matter fell into a number of broad areas includingthin films, multilayers, disordered systems, ultrafine particles, intermetallic compounds,permanent magnets and magnetic imaging techniques.

The development of new techniques for materials preparation has made a dramaticimpact in the area of epitaxial growth of magnetic films. Several presentations have shownthat this process can be controlled on the scale of atomic layers permitting the growth ofartificial structures such as artificial superlattices with nearly atomic resolution. Epitaxialgrowth has also permitted the stabilization of metastable phases in thin films which oftenpossess a strong perpendicular anisotropy which may prove useful for technological

* applications. In magnetic multilayers and superlattices the complex coupling between* different magnetic layers was discussed both experimentally and theoretically. In superlattices

it was proposed that a strong coupling between two ferromagnetic layers can be carried outthrough an intervening layer which is not ferromagnetic. This coupling leads to newproperties not seen in the past. Magnetic surfaces and interfaces show large magnetic

* anisotropy (surface anistropy), coercivity, magnetoresistance, galvanomagnetic andmagnetooptic effects that can lead to future storage technologies. Band structure studies usingstatistical techniques of Monte Carlo calculations, led to accurate calculations of the Curietemperature of Fe, Co, Ni films. The solution of this problem opened the door for otherimportant phenomena which are due to 'spin orbit' coupling. Several contributions discussedthe physics of ultrafine particles and granular solids with interesting and unique propertiesfrom superpararmagnetism to strong magnetic hysteresis. The magnetic properties of rare-earth intermetallic compounds with potential applications in permanent magnets have beendiscussed including the crystal field effects and the origin of magnetic anisotropy. Themagnetic hysteresis behavior of fine particles, permanent magnets, melt-spun ribbons andmechanically alloyed magnets have been discussed. The magnetic hysteresis models of'domain wall pinning' and 'nucleation of reversed domains* have been reviewed and theirapplicability in different magnetic materials was discussed. The micromagnetic approachusing the Landau-Lifshitz-Gilbert equation was also presented to explain the hysteresisbehavior of thin films.

The magnetic properties of all of these materials are strongly influenced by theirmicrostructure and several methods to evaluate their growth, lattice structure and sampleintegrity were discussed. These included spin-polarized electron spectroscopy, DPC andRHEED/RE Microscopy and Lorentz microscopy.

Finally the applications of magnetic materials in magnetic recording, magneto-opticrecording and permanent magnets have been discussed with more emphasis given to theimprovement or material properties for these applications.

I. THIN FILMS, SURFACES AND INTERFACES

1. Electronic Structure and Magnetism of Metal Surfaces, FreemanOverlayers & Interfaces

*2. Metastable Phases Via MBE G. Prinz

3. Spin Resolved Photoemmizon Kirschner

4. Growth and Magnetic Properties of Metastable HeinrichStructures

5. Correlation of Crystalline and Electronic Structure in SchneiderEpitaxial FCC-Cobalt Monolayers on Cu(100)

6. M6ssbauer Studies of Ultrathin Magnetic Films of KoonFe/Ag(100)

7. Spin-Dependence of Absorbed and Reflected Current Hammond

on Fe(1 10)

8. MBE Growth of Metal/Semiconductor Interfaces Slaughter

9. Surface and Interface Magnetism Meier

10. Ferromagnetic Resonance Studies of Epitaxial CelinskiUltrathin Fe(001)/Cu(001) Bilayers andFe(001 )/Cu(001 )/Fe(00 1) Trilayers

11. Laser Ablation Deposition of Metallic Thin Films Gavigan

12. Exchange Coupled Films for Magneto-Optic GambinoApplications

13. Temperature Dependence of Micromagnetic Domain McFadyenStructure in Cobalt Films

14. Hyperfine Interaction Techniques Applied to the Study Rots

of Surfaces and Interfaces

15. Surface Magnetostriction O'Handley

to be sent directly to Plennum Publishing Company

II. MULTILAYERS

1. Magnetic Rare-Earth Artificial Metallic Superlattices Rhyne

2. X-Ray Characterization of Magnetic Multilayers and FalcoSuperlattices

3. The Characterization of Interface Roughness and Sinha

Other Defects in Multilayers by X-Ray Scattering

4. Magnetism of Nanostructured Rare-Earth Multilayers Sellmyer

5. FMR Studies of Metallic Magnetic Thin Films in HurdequintLayered Structures

6. Compositionally Modulated Magnetic Multilayers: FlevarisTemperature and Modulation Dependent Properties

7. Structural and Magnetic Properties of Epitaxial Co/Pd EngelSuperlattices

8. First Principle Calculation of the Magnetocrystalline DaalderopAnisotropy Energy of ConPdm Multilayers

9. Structural and Magnetic Studies in Co-Pt Multilayers Krishnan

10. Magnetic Properties of Hexagonal Fe/Ru Superlattice PiecuchWith Short Periodicities

11. Magnetic Studies of Fe-Si Compositionally Modulated TejadaThin Films

12. M6ssbauer Spectroscopy of the Fe/Ni Interface Donzelli

13. Analysis of Amorphous Dysprosium - Transition Metal ShanNanoscale Magnetic Multilayers

14. Transport Properties of Metallic Thin Films and FertMultilayers

I1. DOMAIN WALLS, MAGNETIC DOMAINS AND TECHNIQUES FOR THEIR OBSERVATION

1. Micromagnetics of Longitudinal Recording Media Alexopoulos

2. MO-Recording: The Switching Process and Its MergelRelation to the Magnetic Properties of Thin Films

3. Micromagnetic Computations of Magnetization Jakubovics

Configurations

4. Domain Walls and Domain Wall Structure Humphrey

5. Domain Wall Multiplication in Amorphous BeatriceFerromagnetic Alloys

6. Electron Microscope Methods for Imaging Internal SpenceMagnetic Fields at High Spatial Resolution

7. Scanning Tunneling Microscopy and Force Microscopy Garcia

Applied to Magnetic Materials

8. Special Session on Spin-Polarized Vacuum Tunneling Notes by Hathaway

9. Magnetic Imaging Via Scanning Electron Microscopy Celottawith Polarization Analysis

10. Atomic Scale Probe Into High-Tc Superconductors RaoUsing Scanning Tunneling Microscopy

IV. MAGNETIC ANISOTROPY AND RANDOM MAGNETS

1. Magnetic Anisotropy Jansen

2. Random Anisotropy in Magnetic Materials Cullen

3. Perpendicular and In-Plane Anisotropy in Amorphous O'SheaTb-Fe

4. Magnetostriction in Amorphous Magnets Hernando

5. Anderson Localization in 3-Dimensional Amorphous FilippiAlloys: Evolution with the Content of Magnetic Ions

6. On the Law of Approach to Saturation in the Series of AmaralAmorphous Alloys oc-Dy.Gd-..Ni

7. Magnetoresistance of Amorphous U,-SbX Films Freitas

8. Absence of Temperature-Driven First Order Phase BerkerTransitions in Systems with Random Bonds

V. MAGNETIC SEMICONDUCTORS AND INTERMETALLIC COMPOUNDS

1. Magnetic Behavior of Diluted Magnetic de JongeSemiconductors

2. Intermetallic Compounds and Crystal Field CoeyInteractions

3. Crystal Field and Exchange Interactions in Hard Franse

Magnetic Materials

4. First Order Magnetization Processes Asti

5. Structure and Properties of Novel Ternary Fe-RichRare-Earth Carbides Jacobs

VI. FINE PARTICLES

1. Granular Solids Chien

2. Ultrafine Magnetic Particles Hadjipanayis

3. Magnetic Nanometer Systems and M6ssbauer MorrishSpectroscopy

4. Some Topics in Fine Particle Magnetism Berkowitz

5. Massbauer Studies of Fine Fe-Based Particles Morup

6. M6ssbauer Studies of Fine Particles of Fe-Cr-B Kostikas

7. Chemical Preparation of Fe-Cr-B Particles Koch

8. Composition and Structure of Fe-Ni-B Alloy Particles LinderothPrepared by Chemical Reductions with NaBH 4

9. Quantum Effects in Ultrafine Nd-Fe-B Particles Quintela

10. Magnetization Reversal in Clusters of Magnetic HendriksenParticles

11. Electric and Magnetic Properties of Small Systems Arajs

12. Existence of Frequency Cut-Off in the Spin Wave GarciaSpectrum of Small Magnetic Particles

VII. MAGNETIC HYSTERESIS AND PERMANENT MAGNETS

1. Mechanically Alloyed Permanent Magnets Schultz

2. Melt-Spun Magnets Pinkerton

3. Solid NdFeB Magnets Made by Gas Atomization and DulisExtrusion

4. The Role of Microstructure in Permanent Magnets Hadjipanayis

S. Lorentz Micrt,,copy in Permanent Magnets Fidler

6. Coercivity in Hard Magnetic Materials Givord

7. Micromagnetism and Magnetization Processes in KronmfillerModern Magnetic Materials

8. Micromagnetic Approach to Magnetic Hysteresis Victora

9. Magnetic Hystczesis in Disordered Magnets Soukoulis

10. Coercivity of Nanostructured Materials Otani

11. Magnetic Hysteresis of Co-Pt Films Tsoukatos

12. Technology and Application of Permanent Magnets Narasimhan

LECTURERSProfessor J. Kirschner

Professor C. Chien Institut fur GrenzflachenforschungJohns Hopkins University and VakuumphyiskDepartment of Physics KFA JulichBaltimore, MD 21218 WEST GERMANY

Professor T. Coey Professor K. KronmullerDepartment of Pure & Applied Physics Max-Planck Inst. fur MetallforschungTrinity College Institut fur PhysikDublin 2 Heisenbergstrasse 1IRELAND 7000 Stuttgard 80

WEST GERMANYProfessor J. CullenNaval Surface Weapons Center Professor A. MorrishSilver Springs, MD 20901-5900 Department of Physics

University of ManitobaProfessor W. deJong Winnepeg, MAN R3T 2N2Department of Physics CANADAEindhoven University of Technologyde Dolech 2 Dr. G. PrinzNL-5600 MB Eindhoven Naval Research LaboratoryNETHERLANDS Washington, DC 20390

Professor A. Fert Professor J. RhyneLaboratoire de Physique des Solides National Bureau of StandardsUniversite Paris Sud Gaithersburg, MD 20899F91405 Orsay, FRANCE

Professor D. SellmyerProfessor N. Garcia Department of PhysicsDepartment of Physics University of NebraskaAutonouous University of Madrid Lincoln, NE 68588Madrid, SPAIN

Professor J. SpenceProfessor D. Givord Department of PhysicsNeel Laboratory Arizona State UniversityCNRS 166X-38042 Tempe, AZ 85287Grenoble, CEDEXFRANCE

Professor G. HadjipanayisUniversity of DelawareDepartment of Physics & AstronomyNewark, DE 19716

Professor H. JansenDepartment of PhysicsOregon State UniversityCorvallis, OR 97331

Professor V. Amaral Dr. 0. DonzelliCentro de Fisica de Universidade Dipartimento di Fisica

de Porto Universita (GNSM-CISM)4000 Porto via Paradiso 12PORTUGAL 44100 Ferrara

ITALYDr. P. AlexopoulosIBM Almaden Research Center Dr. E. Dulis650 Harry Road Crucible Research Inc.San Jose, CA 95120-6099 Pittsburgh, PA 15212

Dr. S. AraJs Dr. C. FalcoDepartment of Physics Optical Science CenterClarkson University & Physics Dept.Potsdam, NY 13676 University of Arizona

Tucson, AZ 85721Dr. G. AstiInstitute MASPEC del C.N.R. Dr. J. Fidlervia Chiavari, 18 A, 43100 Parma Technical Uni-ersitat WienITALY Wiederer Hausptstrasse 8-10

A-104 WienDr. N. Berker AUSTRIAMITPhysics Department Professor P.J.P. FreitasCambridge, MA 02139 INESC, rua Alves Redol 9

Apartado 10105Dr. A. Berkowitz 1017 Lisboa CodexMail Code R-001 PORTUGALCenter for Magnetic RecordingUniveristy of CA - San Diego Dr. J. J. M. FranseLa Jolla, CA 92093 Natuurkunding Laboratorium

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& Technology THE NETHERLANDSGaithersburg, MD 20899

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des Solides MITUniversite Paris Sud 77 Massachusetts Avenue91405 Orsay Cambridge, MA 02139FRANCE

Dr. M. O'SheaMrs. T. H. Jacobs Department of PhysicsKamerlingh Onnes Lab Cardwell HallUniversity of Leiden Kansas State University2300 RA Leiden Manhattan, KS 66506THE NETHERLANDS

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of Materials CRPAM-BP 109University of Oxford 54704 Pont-A-Mousson CEDEXParks Road, Oxford OX1 3PH FRANCEENGLAND

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de PortoDr. L. Shultz 4000 PortoSiemens, AG Research Labs. PORTUGALD-8520 ErlangenFEDERAL REPUBLIC OF GERMANY Professor F. Badia

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Dr. C. Soukoulis Dr. T. BakasDepartment of Physics Univeristy of IoanninaIowa State University P.O.B. 1186Ames, IA 50010 OR-451 10 Ioannina, GREECE

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Mr. P. BelienUniversity of Leuven

Dr. R. H. Victora Department of PhysicsDiversified Technologies Div. Celestijnenlaan 200 DResearch Laboratories B-3030 Leuven, BELGIUMEastman Kodak Co.Rochester, NY 14650 Mr. M. Carey

Center for Magnetic Recording Res.Univ. of California, San DiegoLa Jolla, CA 92093

Dr. Z. CelinskiDepartment of PhysicsSimon Fraser UniversityBurnaby VSA IS6BRITISH COLUMBIA

Mr. J. ChildressJohns Hopkins UniversityDepartment of Physics

Baltimore, MD 21218

Mr. J. GuzmanMr. C. Christides Magnetics Technology CenterInstitute of Materials Science Carnegie Mellon UniversityDEMOKRITOS N.R.CPS Pittsburgh, PA 15213Ag. Paraskevi, Attiki, GREECE

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AT

Dr. S. Linderoth Dr. D. NiarchosLab. of Applied Physics Demokritos National Research CenterTechnical University of Denmark 153 10 Ag. Paraskeri AttikisDK-2800, Lyngby P.O.B. 60228DENMARK GREECE

Dr. R. McCallum Mr. J. NoguesAmes Lab, 106 Wilhelm Hall Department of Solid St. PhysicsIowa State University Royal Inst. of Tech.Ames, IA 50011 S-100 44, Stockholm, SWEDEN

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Professor C. Mavroyamnnis Ms. H. PontDivision of Chemistry Departamento de FisicaNational Research Council of Canada Universitat Autonoma BarcelonaOttawa, Ontario, Canada KlA OR6 08193 Bellaterr SPAIN

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Professor E. Ribas Mr. E. SingletonDept. de Fisica Fonamental University of DelawareUniversitat de Barcelona Dept. of Physics & AstronomyDiagonal 647, E-08028 SPAIN 223 Sharp Lab08028 Barcelona, SPAIN Newark, DE 19716

Dr. J. Schmidt Dr. S. SinhaInst. de Fisica-UFRGS Physics DepartmentCx. Postal 15051 Brookhaven National LabPorto Alegre, RS 91500 BRAZIL Upton, NY 11973

Professor C. Schneider Mr. S. SladeFreeie Universitat Berlin University of California-San DiegoFachbereich Physik Center for Magnetic RecordingInstitut fur Atom under R-0O01

Festkorperphysik (WE 1) La Jolla, CA 92093Arminallee 14, D-1000Berlin 33 Dr. J. SlaughterFEDERAL REPUBLIC OF GERMANY Department of Physics

Building 81Dr. I. Shah University of ArizonaE. I. duPont Experimental Station Tucson, AZ 85721P.O. Box 80356Wilmington, DE 19880-0356 Dr. M. Solzi

Instituto Materiali SpecialiMr. Z. Shan Per Elettronica E. MagnetismDept. of Physics & Astronmy MASPECBehlen Lab 43100 Parma, ITALYLincoln, NE 68588

Professor J. SousaDr. B. Siberchicot Centro de Fisica de Universidade deBoite Postale 27 Porto94190-Villeneuve St. Georges 4000 PortoFRANCE PORTUGAL

Dr. W. Simmons Professor C. StassisChief Materials Branch Iowa State UniversityU.S. Army Research Department of PhysicsDevelopment & Standardization Group Ames, IA 50011Edison House, 223 Old Marylebone Rd.London NW11 5th Dr. J. TeterENGLAND R43, Naval Surface Warfare Center

Silver Springs, MD 20905-5000Dr. T. SimopoulosDemokritos National Research Center Dr. F. TezerInst. of Materials Science Physics Department153 10 Ag. Paraskerl Attikis Hacettepe UniversityP.O.B. 60228 Beytepe, AnkaraGREECE TURKEY 06532

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Dr. C. WilliamsCode 6346U.S. Naval Research LaboratoryWashington, DC 20375-5000

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