Beaurepaire / Bulou / Scheurer Magnetism and Synchrotron Radiation

New Trends
1. Auflage 2010
ISBN: 978-3-642-04498-4
Verlag: Springer
Format: PDF
Kopierschutz: Wasserzeichen (»Systemvoraussetzungen)

E-Book, Englisch, 421 Seiten

Advances in the synthesis of new materials with often complex, nano-scaled structures require increasingly sophisticated experimental techniques that can probe the electronic states, the atomic magnetic moments and the magnetic microstructures responsible for the properties of these materials. At the same time, progress in synchrotron radiation techniques has ensured that these light sources remain a key tool of investigation, e.g. synchrotron radiation sources of the third generation are able to support magnetic imaging on a sub-micrometer scale. With the Fifth Mittelwihr School on Magnetism and Synchrotron Radiation the tradition of teaching the state-of-the-art on modern research developments continues and is expressed through the present set of extensive lectures provided in this volume. While primarily aimed at postgraduate students and newcomers to the field, this volume will also benefit researchers and lecturers actively working in the field.

Autoren/Hrsg.

Beaurepaire, Eric

Bulou, Hervé

Scheurer, Fabrice

Jean-Paul, Kappler

Bulou, Herve

Inhaltsverzeichnis

1;Foreword;6
2;Preface;9
3;Contents;11
4;1 Introduction to Magnetism;22
4.1;1.1 Introduction;22
4.1.1;1.1.1 Definition of the Magnetic Moment;22
4.1.2;1.1.2 Energy of the Moment in an External Magnetic Field;23
4.1.3;1.1.3 Further Definitions;24
4.2;1.2 Magnetism of Free Atoms and Electrons;25
4.2.1;1.2.1 Diamagnetism of Free Atoms;25
4.2.2;1.2.2 Paramagnetism of Free Atoms;26
4.2.3;1.2.3 Pauli Paramagnetism of Free Electrons(in Metals);30
4.3;1.3 Ferromagnetism;31
4.3.1;1.3.1 Molecular Field;32
4.3.2;1.3.2 Exchange Interaction as Originof the Molecular Field;33
4.3.3;1.3.3 Mean Field Approximation (MFA);35
4.3.3.1;1.3.3.1 Curie Temperature in MFA;36
4.3.3.2;1.3.3.2 Curie–Weiss Law ;37
4.3.3.3;1.3.3.3 The Behavior of M(T) Close to Tc;37
4.3.4;1.3.4 Spin Waves;39
4.3.4.1;1.3.4.1 Dispersion Relation of Spin Waves;40
4.3.4.2;1.3.4.2 Thermal Excitation of Spin Waves;41
4.3.5;1.3.5 Itinerant Ferromagnetism;42
4.4;1.4 Magnetization Curves M(H);43
4.4.1;1.4.1 Magnetostatic Energy or Shape Anisotropy;44
4.4.2;1.4.2 Magneto-Crystalline Anisotropy;45
4.4.3;1.4.3 Magnetization Curves in the ``Uniform Rotation'' Model;47
4.4.3.1;1.4.3.1 =0 Case;48
4.4.3.2;1.4.3.2 =45 case;48
4.4.3.3;1.4.3.3 =90 case;49
4.4.4;1.4.4 Domains and Domain Walls;49
4.4.4.1;1.4.4.1 Why Do Domains Exist?;50
4.4.4.2;1.4.4.2 Domain Wall Width;51
4.4.4.3;1.4.4.3 Nucleation of Reversed Domains;52
4.4.4.4;1.4.4.4 Pinning of Domain Walls;52
4.4.4.5;1.4.4.5 Bloch or Néel Wall?;53
4.4.4.6;1.4.4.6 Why Small Particles are Always Mono-domain?;54
4.4.4.7;1.4.4.7 Superparamagnetism ;54
4.5;1.5 Thin Film Magnetism;56
4.5.1;1.5.1 Surface Anisotropy;56
4.5.2;1.5.2 Indirect Exchange Coupling in Multilayers;57
4.5.3;1.5.3 Giant Magnetoresistance;60
4.6;References;61
5;2 Spintronics: Conceptual Building Blocks;63
5.1;2.1 Spin Precession;63
5.2;2.2 Spin Relaxation;65
5.3;2.3 Spin-dependent Transport: The Collinear Case;68
5.3.1;2.3.1 Collisions;70
5.3.2;2.3.2 Calculation of the Currents;72
5.3.3;2.3.3 Diffusion Equation and the SpinAccumulation;75
5.4;2.4 Spin Relaxation of Conduction Electrons;79
5.4.1;2.4.1 Spin-Lattice Relaxation Timefor Conduction Electrons;79
5.4.2;2.4.2 The Bottleneck Regime;82
5.4.3;2.4.3 Spin–Orbit Scattering;83
5.4.4;2.4.4 Electron–Magnon Scattering;85
5.4.5;2.4.5 Spin Mixing by Collisions with Magnons;87
5.5;2.5 Spin-dependent Transport: The Non-collinear Case;90
5.5.1;2.5.1 Toward a Semi-classical Descriptionof Spin Dynamics in Transport;91
5.5.2;2.5.2 Constitutive Equations;91
5.5.3;2.5.3 Spin Diffusion in Non-collinear Configurations;93
5.5.4;2.5.4 Domain Walls;94
5.6;References;95
6;3 Interaction of Polarized Light with Matter;97
6.1;3.1 Introduction;97
6.2;3.2 Experimental Observations of X-Ray Interaction with Matter ;98
6.2.1;3.2.1 Absorption;98
6.2.2;3.2.2 Dependence on Energy;98
6.2.3;3.2.3 Dependence on the Atomic Environment;100
6.2.4;3.2.4 Dependence on the Light Polarization;100
6.2.5;3.2.5 Diffraction Around Edges;101
6.3;3.3 The Light;103
6.3.1;3.3.1 Definitions and Notations;103
6.3.2;3.3.2 Stokes Parameters;104
6.3.3;3.3.3 Quantization of the Electromagnetic Field;105
6.4;3.4 Interaction of Light with an Electron in an Atom;105
6.4.1;3.4.1 Linear and Nonlinear Interactions;106
6.4.2;3.4.2 Interaction Hamiltonian;106
6.4.3;3.4.3 Absorption and Emission;108
6.4.4;3.4.4 Scattering;108
6.4.4.1;3.4.4.1 Thomson Scattering;109
6.4.4.2;3.4.4.2 Compton Scattering;110
6.4.4.3;3.4.4.3 Resonant Scattering;111
6.4.4.4;3.4.4.4 Nonresonant Magnetic Scattering;112
6.4.5;3.4.5 Transition Matrix;113
6.4.6;3.4.6 Selection Rules;114
6.4.6.1;3.4.6.1 Final States;114
6.4.6.2;3.4.6.2 Initial States;115
6.4.6.3;3.4.6.3 Operator;116
6.4.6.4;3.4.6.4 The Transition Matrix;117
6.5;3.5 Dielectric Function or Macroscopic Point of View;118
6.5.1;3.5.1 Complex Permittivity;119
6.5.2;3.5.2 Complex Refractive Index;121
6.6;3.6 X-Ray Spectroscopies;122
6.6.1;3.6.1 Characteristic Times;123
6.6.2;3.6.2 The Different Spectroscopies;124
6.6.2.1;3.6.2.1 Real Absorption;124
6.6.2.2;3.6.2.2 Virtual Absorption;126
6.6.3;3.6.3 Fluorescence and Auger Spectroscopies;126
6.6.4;3.6.4 XANES and RXS Formula;127
6.6.4.1;3.6.4.1 Relation with the Density of States;130
6.6.5;3.6.5 Multipole Analysis;132
6.6.5.1;3.6.5.1 Cartesian Tensors;132
6.6.5.2;3.6.5.2 Spherical Tensors;134
6.6.5.3;3.6.5.3 m3m Symmetry (Oh);136
6.6.5.4;3.6.5.4 4/mmm Symmetry (D4h);136
6.6.5.5;3.6.5.5 4/m'm'm Symmetry;137
6.6.6;3.6.6 X-Ray Magnetic Circular Dichroism;138
6.7;3.7 Monoelectronic Simulations;140
6.7.1;3.7.1 The Potential;140
6.7.2;3.7.2 The Multiple Scattering Theory;141
6.7.3;3.7.3 Available Codes;143
6.8;3.8 Conclusion;143
6.9;References;144
7;4 Synchrotron Radiation Sources and Optical Devices;146
7.1;4.1 Optics for UV and X-Ray;146
7.2;4.2 Sources, Beamlines, and Monochromatorsfor Soft X-Ray;152
7.2.1;4.2.1 SR Sources and Prefocusing or Heat LoadSection;152
7.2.2;4.2.2 Soft X-Ray Monochromators and Diffraction Gratings;157
7.2.3;4.2.3 Refocusing Optics;161
7.3;References;162
8;5 X-Ray Magnetic Dichroism;164
8.1;5.1 Introduction;164
8.2;5.2 X-Ray Absorption Spectroscopy;165
8.2.1;5.2.1 X-Ray Absorption Near-Edge Structure;166
8.2.2;5.2.2 Dichroism in X-Ray AbsorptionSpectroscopy;167
8.3;5.3 X-Ray Magnetic Circular Dichroism;168
8.3.1;5.3.1 Determination of Orbital and Spin Magnetic Moments: Sum Rules;169
8.4;5.4 Experimental Setup;171
8.5;5.5 Data Analysis;171
8.5.1;5.5.1 Self-absorption and Saturation Effects in Electron Yield;171
8.5.2;5.5.2 Standard Analysis;173
8.6;5.6 Examples of Recent Research;174
8.6.1;5.6.1 Failure of Sum Rule-based Analysis for Light 3d Elements;175
8.6.2;5.6.2 Spin-dependence of Matrix Elements in Rare Earths;178
8.6.3;5.6.3 Paramagnetic Biomolecules on Ferromagnetic Surfaces;181
8.7;5.7 Conclusions and Outlook;184
8.8;References;185
9;6 X-Ray Detected Optical Activity;187
9.1;6.1 Introduction;187
9.2;6.2 X-Ray Detected OA Tensor Formalism;189
9.3;6.3 Instrumentation and Experimental Considerations;191
9.4;6.4 Natural Optical Activity Detected with X-Rays;194
9.4.1;6.4.1 X-Ray Natural Circular Dichroism;194
9.4.2;6.4.2 Vector Part of X-Ray-detected OA;198
9.5;6.5 Nonreciprocal X-Ray-detected OA;200
9.5.1;6.5.1 Nonreciprocal X-Ray Linear Dichroism;200
9.5.2;6.5.2 X-Ray Magnetochiral Dichroism: XMD;202
9.6;6.6 Effective Operators for X-Ray Detected OA;204
9.7;References;206
10;7 X-Ray Detected Magnetic Resonance: A New Spectroscopic Tool;209
10.1;7.1 Introduction;209
10.2;7.2 Precession Dynamics Probed with X-Rays ;211
10.2.1;7.2.1 Phenomenological Equation of Motion;211
10.2.2;7.2.2 Precession Dynamics of Orbital and Spin Magnetization Components;213
10.2.3;7.2.3 Precession Under High Pumping Power;214
10.2.3.1;7.2.3.1 Foldover Effects;214
10.2.3.2;7.2.3.2 Suhl's Instability Thresholds;216
10.2.4;7.2.4 Nonuniform Eigen Modes of Precession;217
10.2.5;7.2.5 Longitudinal and Transverse RelaxationTimes;220
10.3;7.3 Experimental Results;221
10.3.1;7.3.1 Ferrimagnetic Iron Garnets;221
10.3.2;7.3.2 Modular XDMR Spectrometer;223
10.3.3;7.3.3 XDMR in Longitudinal Geometry;225
10.3.3.1;7.3.3.1 Detection Issues;225
10.3.3.2;7.3.3.2 Element-selective Measurements on YIG Films;225
10.3.3.3;7.3.3.3 Collective Effects in the Precession Dynamics of Orbital Components;228
10.3.3.4;7.3.3.4 Direct Estimate of the Longitudinal Relaxation Time T1 ;229
10.3.4;7.3.4 XDMR in Transverse Geometry;231
10.3.4.1;7.3.4.1 Super-Heterodyne Detection;231
10.3.4.2;7.3.4.2 Transverse XDMR Spectra of a YIG/GGG Thin Film Rotated at the Magic Angle;232
10.3.4.3;7.3.4.3 Transverse XDMR Spectra of a Ferrimagnetic Single Crystal of GdIG Above and Below the Compensation Temperature;235
10.4;7.4 Facing New Challenges;238
10.5;References;239
11;8 Resonant X-Ray Scattering and Absorption;241
11.1;8.1 Absorption and Scattering: The Optical Theorem;241
11.2;8.2 Symmetry and X-Ray Absorption;242
11.3;8.3 X-Ray Scattering and Multipole Matrix Elements;244
11.4;8.4 Cartesian Tensors, Magnetism and Anisotropy;246
11.5;8.5 Neumann's Principle and Symmetry-restrictedTensors;249
11.6;8.6 Scattering Matrix and Stokes Parameters;250
11.7;8.7 Diffraction Intensity and the Unit-Cell StructureFactor;252
11.8;8.8 Magnetic Symmetry, Propagation Vector, and the Magnetic Structure Factor;253
11.9;8.9 Crystal Coordinates and Azimuthal Rotations;256
11.10;8.10 Spherical and Cartesian Tensors;257
11.11;8.11 Example: HoFe2;260
11.12;8.12 Example: ZnO;266
11.13;8.13 Example: Ca3Co2O6;271
11.14;8.14 Conclusions;279
11.15;References;279
12;9 An Introduction to Inelastic X-Ray Scattering;281
12.1;9.1 Introduction;281
12.2;9.2 Theoretical Concepts;282
12.2.1;9.2.1 Overview of the IXS Process;282
12.2.2;9.2.2 Interaction Hamiltonian;283
12.2.3;9.2.3 IXS Cross Sections and Fermi Golden Rule;284
12.2.4;9.2.4 Nonresonant IXS;284
12.2.4.1;9.2.4.1 Cross Section;284
12.2.4.2;9.2.4.2 Expressions of the Dynamical Structure Factor;285
12.2.4.3;9.2.4.3 X-Ray Raman scattering: Equivalence with Absorption;286
12.2.5;9.2.5 RIXS;287
12.3;9.3 Applications of IXS;289
12.3.1;9.3.1 Extreme Conditions;289
12.3.1.1;9.3.1.1 Absorption Edge of Light Elements Under Pressure;289
12.3.1.2;9.3.1.2 Magnetic Collapse in Transition Metal;290
12.3.1.3;9.3.1.3 Valence Transition and Kondo Behavior;291
12.3.2;9.3.2 Strongly Correlated Materials;292
12.3.2.1;9.3.2.1 dd-excitations in Transition Metal Oxides;292
12.3.2.2;9.3.2.2 Phonons in Plutonium;294
12.4;9.4 Conclusion;295
12.5;References;295
13;10 XAS and XMCD of Single Molecule Magnets;296
13.1;10.1 Introduction;296
13.2;10.2 Single Molecule Magnets;298
13.2.1;10.2.1 Building Up a Large Spin;298
13.2.2;10.2.2 Magnetic Anisotropy in Single MoleculeMagnets;301
13.2.3;10.2.3 The Dynamics of the Magnetization;304
13.3;10.3 Deposition of Single Molecule Magnets on Surfaces;309
13.4;10.4 XAS and XMCD of SMMs;312
13.4.1;10.4.1 XAS and XMCD to Investigate the Electronic Structure of Mn12 Clusters;313
13.4.2;10.4.2 XAS and XMCD of Monolayers of Mn12SMMs;315
13.4.3;10.4.3 XMCD and Magnetic Anisotropy;318
13.4.4;10.4.4 XMCD and the Dynamics of the Magnetization;322
13.5;10.5 Conclusions;324
13.6;References;325
14;11 Magnetic Structure of Actinide Metals;329
14.1;11.1 Introduction;329
14.2;11.2 Volume Change Across the Actinide Series;331
14.2.1;11.2.1 Photoemission Spectroscopy's Two Cents;332
14.3;11.3 The Six Crystal Allotropes of Pu Metal;333
14.3.1;11.3.1 Lowering the Electronic Energy Through a Peierls-like Distortion;334
14.3.2;11.3.2 Comparison with Cerium;335
14.3.3;11.3.3 Stabilized -Plutonium;336
14.4;11.4 Revised View of the Periodic Table;337
14.5;11.5 Actinide Magnetism;339
14.5.1;11.5.1 Experimental Absence of Magnetic Moments in Plutonium;339
14.5.2;11.5.2 Looking to Other Elements for Clues;341
14.6;11.6 Experimental Complications of Plutonium;341
14.7;11.7 One Man's Electron Energy Loss is Another'sX-Ray Absorption;342
14.8;11.8 Theory;343
14.8.1;11.8.1 Atomic Interactions;343
14.8.1.1;11.8.1.1 Electrostatic Interactions;344
14.8.1.2;11.8.1.2 Spin–Orbit Interaction;345
14.8.2;11.8.2 LS- and jj-Coupling Schemes;346
14.8.2.1;11.8.2.1 LS Coupling;346
14.8.2.2;11.8.2.2 jj Coupling;346
14.8.2.3;11.8.2.3 Transformation Matrix;346
14.8.2.4;11.8.2.4 LS- vs. jj-Coupled Ground State: Example for f2;347
14.8.3;11.8.3 Intermediate Coupling;348
14.8.4;11.8.4 Moments for f2;349
14.8.4.1;11.8.4.1 Spin–Orbit Expectation Value;349
14.8.4.2;11.8.4.2 Orbital and Spin Magnetic Moments;350
14.9;11.9 Spectral Calculations;351
14.10;11.10 Spin–Orbit Interaction and Sum Rule Analysis;352
14.11;11.11 Validity of the Sum Rule;353
14.12;11.12 Experimental Results for the N4,5 Edges;355
14.12.1;11.12.1 What Our Results Mean for Pu Theory;357
14.13;11.13 Conclusions;358
14.14;References;358
15;12 Magnetic Imaging with X-rays;361
15.1;12.1 Introduction;361
15.2;12.2 Concepts of Magnetic Imaging Contrast;363
15.2.1;12.2.1 XMCD Image;364
15.2.2;12.2.2 XMLD Images;367
15.2.3;12.2.3 Polarization Control;370
15.2.4;12.2.4 Local Spectra;371
15.2.5;12.2.5 Spatial Resolution;372
15.3;12.3 Realization of the Magnetic Contrastwith Different Microscopes;374
15.3.1;12.3.1 Photoemission Electron Microscope;374
15.3.2;12.3.2 STXM/TXM;375
15.3.3;12.3.3 ``Lensless'' Imaging;377
15.3.4;12.3.4 Combining Scanning Probes with X-Rays;379
15.4;12.4 Summary;380
15.5;References;380
16;13 Domain Wall Spin Structures and Dynamics Probed by Synchrotron Techniques;383
16.1;13.1 Introduction;383
16.2;13.2 Techniques;385
16.3;13.3 Domain Wall Types and Wall Phase Diagrams;385
16.3.1;13.3.1 Theory of Head-to-Head DomainWall Spin Structures;385
16.3.2;13.3.2 Experimental Determination of Head-to-Head Domain Wall Spin Structures;387
16.3.2.1;13.3.2.1 Spin Structures in Ni80Fe20 (Permalloy);387
16.3.3;13.3.3 Further Head-to-Head Domain Wall Types;389
16.3.3.1;13.3.3.1 Complex Wall Types in Permalloy;389
16.3.3.2;13.3.3.2 Domain Wall Spin Structures in Fe3O4 (Magnetite);390
16.4;13.4 Domain Wall Dynamics;392
16.4.1;13.4.1 Field-induced Domain Wall Propagation;393
16.4.2;13.4.2 Current-induced Domain Wall Propagation;393
16.4.3;13.4.3 Field- and Current-induced Domain WallExcitations;396
16.4.3.1;13.4.3.1 Field-induced Dynamic Wall Deflection;397
16.5;13.5 Summary ;398
16.6;References;398
17;14 Dynamics of Mesoscopic Magnetic Objects;401
17.1;14.1 Introduction;401
17.2;14.2 Macroscopic vs. Mesoscopic Magnetic Objects;402
17.2.1;14.2.1 Magnetic Interactions and Domains;402
17.2.2;14.2.2 Magnetic Time Scales;404
17.2.3;14.2.3 Magnetic Length Scales;405
17.2.4;14.2.4 Landau–Lifshitz–Gilbert Equation;405
17.2.5;14.2.5 Experimental Techniques;407
17.3;14.3 Dynamics in Simple Squares;408
17.3.1;14.3.1 Static Mesoscopic Structures;408
17.3.2;14.3.2 Pulsed Field Excitations;410
17.3.2.1;14.3.2.1 Sequence of Dynamics;410
17.3.2.2;14.3.2.2 Coherent Domain Precession ;411
17.3.2.3;14.3.2.3 Tuning the Response of Mesoscopic Magnetic Objects using Defects;413
17.4;14.4 Vortex Dynamics and Switching;415
17.4.1;14.4.1 Current Induced Resonant Vortex CoreMotion;415
17.4.2;14.4.2 Bistable Configurations by Pinning the Vortex Core;417
17.4.3;14.4.3 Resonant Burst Switching;418
17.5;14.5 Summary;419
17.6;References;420
18;15 From Third- to Fourth-Generation Light Sources: Free-Electron Lasers in the UV and X-ray Range;422
18.1;15.1 Introduction;422
18.2;15.2 The SASE Process and Short-wavelengthFree-Electron Lasers;424
18.3;15.3 First Results at FLASH and the Science Casefor X-Ray FELs;426
18.4;15.4 The Quest for Hard X-Ray FELs;429
18.5;15.5 Seeded Free-Electron Lasers;432
18.6;References;433
19;Contributors;435