Magnetic Properties of Antiferromagnetic Oxide Materials: Surfaces, Interfaces, and Thin Films

Magnetic Properties of Antiferromagnetic Oxide Materials......Page 5
Contents......Page 7
Preface......Page 13
List of Contributors......Page 17
1.1 Introduction......Page 21
1.2 Finite-Size Effects on the Magnetic Ordering Temperature......Page 22
1.3 AFM Anisotropy......Page 26
1.3.2 Dipolar Anisotropy......Page 27
1.4.1 AFM–FM Interface Coupling......Page 29
1.4.2 Coupling between FM Layers Separated by an AFM Oxide Spacer......Page 32
1.5 Micromagnetic Structure at AFM–FM Interfaces......Page 34
1.6 Applications......Page 37
References......Page 38
2.1 Introduction......Page 45
2.2.1 Ultrathin NiO Layers......Page 49
2.2.2 Thick NiO Films......Page 55
2.3.1 Ultrathin CoO Layers......Page 60
2.3.2 Thick CoO Films......Page 63
2.4.1 MnO(001)......Page 67
2.4.2 FeO......Page 68
2.4.3 α-Fe2O3......Page 70
2.5 Oxide–Substrate Interface......Page 73
2.6 Polar-Oxide Surfaces......Page 76
2.7 Conclusions and Perspectives......Page 78
Acknowledgments......Page 80
References......Page 81
3 Dichroism in X-ray Absorption for the Study of Antiferromagnetic Materials......Page 89
3.1 X-ray Absorption and X-ray Dichroism......Page 90
3.1.1 X-ray Magnetic Circular Dichroism in the One-Electron Approximation......Page 91
3.1.1.2 Core-Hole and Other Many-Body Effects......Page 93
3.1.2 XMCD in the Strongly Correlated Limit: Multiplet Effects......Page 95
3.1.2.1 Ligand Field Atomic Multiplet Calculations......Page 96
3.1.2.2 Charge-Transfer Effects......Page 97
3.2.1 Orbital Moment......Page 98
3.2.2 Spin Moment......Page 99
3.2.3 Sum Rule for Linear Dichroism......Page 100
3.3 Experimental Determination of X-ray Absorption......Page 101
3.4 Linear X-ray Dichroism in Rare-Earth Compounds......Page 103
3.4.1 FexTb1-x Amorphous Thin Films......Page 104
3.5.1 Magnetic Linear Dichroism in Thin NiO Films on MgO......Page 106
3.5.1.1 Calculations......Page 107
3.5.1.4 Results......Page 109
3.6 Conclusions......Page 113
References......Page 114
4.1 Introduction......Page 119
4.2.1 Mott-Hubbard and Charge Transfer Insulators......Page 120
4.2.2.1 Independent Electron Ligand Field Theory......Page 121
4.2.3 Spin–Orbit Coupling in Cubic Symmetry......Page 123
4.2.3.1 Single Electron in an Open t2g Shell......Page 124
4.2.3.2 d6 and d7 Configurations......Page 125
4.3.1 Magnetic Ordering of MnO, FeO, CoO and NiO......Page 126
4.3.1.2 FeO and CoO......Page 127
4.4 X-ray Absorption Spectroscopy......Page 128
4.4.1 Magnetic Linear Dichroism......Page 130
4.5 Strain......Page 135
4.6.1 XMLD of Epitaxial NiO(100)/MgO layers......Page 140
4.6.2 Ligand-Field-Induced Linear Dichroism in Strained NiO/Ag(100) Layers......Page 142
4.6.3 Isotropic XAS of CoO......Page 145
4.6.4 Linear Dichroism of Strained CoO Layers......Page 147
4.6.5 Spin Alignment in Strained CoO......Page 151
4.6.6 Electronic Stucture of Strained CoO......Page 152
4.6.7 Strain-Induced Linear Dichroism in MnO Layers......Page 153
Appendix: Polarization and Spin Direction Dependence of the Linear Dichroism in Nonspherical Symmetry......Page 157
References......Page 160
5.1 Introduction......Page 163
5.2.1 Diluted Antiferromagnets in a Magnetic Field......Page 165
5.2.2 Domain-State Model for Exchange Bias......Page 168
5.2.3 Mean-Field Solution of the Domain-State Model......Page 169
5.3.1 Antiferromagnetic Oxides: CoO, Co1-y, Co1-xMgxO......Page 176
5.3.2 Exchange Bias between the Ferromagnet Co and the Diluted Antiferromagnet CoO......Page 181
5.3.2.1 Nonmagnetic Dilution of the Antiferromagnet......Page 182
5.3.2.2 Hysteresis Curves and Uncompensated Magnetic Moments (Vertical Shift)......Page 184
5.3.2.3 Substitutional versus Structural Defects......Page 185
5.3.2.4 Temperature Dependence......Page 187
5.3.2.5 Thermoremanent Magnetization and Training Effect......Page 190
5.3.2.6 Cooling-Field Dependence......Page 193
5.3.2.7 Antiferromagnetic Thickness Dependence......Page 194
5.3.2.8 Blocking Temperature Distribution......Page 195
5.4.1 Modeling of Experimental Data......Page 198
5.4.2 Anisotropy Dependence......Page 201
5.4.3 Structural Dependence......Page 203
5.5 Conclusions......Page 206
References......Page 207
6.1 Introduction......Page 211
6.2.1 Uncompensated Surface of the Antiferromagnet......Page 212
6.2.2 Compensated Surface of the Antiferromagnet......Page 214
6.3 Mathematical Model......Page 215
6.4 The Interface between Thick Ferromagnet–Antiferromagnet Layers......Page 216
6.4.1.1 R << (Δf, Δaf)......Page 217
6.4.1.2 R >> (Δf, Δaf)......Page 220
6.4.2 Compensated Surface of the Antiferromagnet......Page 221
6.5.1.1 The Case of γaf >> 1......Page 226
6.5.1.2 A Thin Layer with a Much Higher Exchange Rigidity......Page 233
6.5.2 Compensated Surface of an Antiferromagnetic Substrate......Page 238
6.6 Spin-Valve Ferromagnet–Antiferromagnet–Ferromagnet System......Page 239
6.6.1 Domain Walls in a Three-Layer System......Page 240
6.6.1.1 γf, af a/γaf << 1......Page 241
6.6.2.3 γf, af a/γaf >> 1\n......Page 242
6.6.2 Phase Diagram......Page 246
6.6.3 Matching Experimental Data?......Page 253
References......Page 256
7.1 Introduction......Page 259
7.2 Interface and Structural Effects......Page 260
7.2.1 Chemical and Structural Quality Effects......Page 262
7.2.2.1 Reduced Magnetization and ‘‘Dead’’ Layers at the Interface......Page 264
7.2.2.2 Anisotropy and Interface Anisotropy of Thin Fe3O4 Layers......Page 266
7.2.2.3 The Interface Structure: Antiphase Boundaries......Page 270
7.3.1.1 AF–NM Multilayers: Finite-Size Scaling......Page 278
7.3.1.2 AF–AF Multilayers: Exchange Coupling......Page 281
7.3.2.1 Exchange Anisotropy......Page 283
7.3.2.2 Dependence on Antiferromagnetic Thickness......Page 286
7.3.2.3 Perpendicular Coupling......Page 289
7.3.2.4 Reduction of the Blocking Temperature......Page 294
7.3.3.1 Coupling across a Nonmagnetic Layer......Page 297
7.3.3.2 Coupling across an Antiferromagnetic Layer......Page 301
7.3.4 Perpendicular Anisotropy......Page 303
7.4.1 Magnetoresistance Effects......Page 305
7.4.1.1 Tunnel Junctions using Fe3O4–MgO......Page 306
7.4.1.3 Tunnel Junctions using Fe3O4–oxide–LSMO......Page 307
7.4.1.4 Tunnel Junctions using a CoFe2O4 Spin Filter......Page 308
7.4.2 Magnetooptical Effects......Page 309
7.5 Conclusions and Outlook......Page 310
References......Page 311
8.1 Introduction......Page 321
8.1.1 Origin of Antiferromagnetic Domains......Page 322
8.1.2 Soft X-Ray Spectroscopy......Page 326
8.1.3 Photoemission Electron Microscope......Page 328
8.1.4 Soft X-Ray Dichroism......Page 330
8.2.1 Imaging Antiferromagnetic Domains and Domain Walls......Page 333
8.2.2 Magnetism and Crystallography......Page 337
8.3 Antiferromagnetic Domains in Exchange-Coupled Systems......Page 338
8.3.1 Antiferromagnetic–Ferrmagnetic-Exchange Coupling......Page 339
8.3.2 Magnetic Domains at Interfaces of Antiferromagnets with Ferromagnets......Page 342
8.3.3 Origin of Spin Reorientation......Page 347
8.4 Temperature Dependence of the Antiferromagnetic Domain Structure......Page 349
8.5.1 A Quick Look at a Fluoride......Page 353
8.5.2 Magnetic Reversal Mechanism on the Microscopic Scale......Page 355
8.6 Summary and Outlook......Page 357
References......Page 358
Index......Page 361