Handbook of Magnetic Materials

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Handbook of Magnetic Materials, Volume 26, covers the expansion of magnetism over the last few decades and its applications in research, notably the magnetism of several classes of novel materials that share the presence of magnetic moments with truly ferromagnetic materials. The book is an ideal reference for scientists active in magnetism research, providing readers with novel trends and achievements in magnetism. Each article contains an extensive description given in graphical, as well as, tabular form, with much emphasis placed on the discussion of the experimental material within the framework of physics, chemistry and material science.

Comprises topical review articles written by leading authorities
Includes a variety of self-contained introductions to a given area in the field of magnetism without requiring recourse to the published literature
Introduces given topics in the field of magnetism
Describes novel trends and achievements in magnetism

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Front Cover 2
Handbook of Magnetic Materials 5
Copyright 6
Contents 7
List of Contributors 11
Preface 13
Contents of Volumes 1–25 15
Chapter 1: Magnetic Relaxation of Lanthanide-Based Molecular Magnets 23
- 1. Introduction 24
- 2. Electronic Structure, Magnetism, and Relaxation of Lanthanide Ions 28
  - 2.1. Electronic Structure of the Lanthanides 28
    - 2.1.1. Single Ion: Configuration, Levels, and Terms 29
    - 2.1.2. Magnetism of the Isolated Ion 30
    - 2.1.3. Crystal Field Interaction 31
    - 2.1.4. The Role of Symmetry 33

Front Cover 2
Handbook of Magnetic Materials 5
Copyright 6
Contents 7
List of Contributors 11
Preface 13
Contents of Volumes 1–25 15
Chapter 1: Magnetic Relaxation of Lanthanide-Based Molecular Magnets 23
- 1. Introduction 24
- 2. Electronic Structure, Magnetism, and Relaxation of Lanthanide Ions 28
  - 2.1. Electronic Structure of the Lanthanides 28
    - 2.1.1. Single Ion: Configuration, Levels, and Terms 29
    - 2.1.2. Magnetism of the Isolated Ion 30
    - 2.1.3. Crystal Field Interaction 31
    - 2.1.4. The Role of Symmetry 33
    - 2.1.5. The Kramers Theorem 34
    - 2.1.6. The Griffith Theorem 34
  - 2.2. Mechanisms of Magnetic Relaxation of Molecules 34
    - 2.2.1. The Spin-Phonon Interaction 36
    - 2.2.2. Direct Process 36
    - 2.2.3. Raman Process 38
    - 2.2.4. Orbach Process 39
    - 2.2.5. The Bottleneck Effect 40
      - 2.2.5.1. PB in High-Temperature Regime 41
      - 2.2.5.2. PB in Low-Temperature Regime: RPT 42
    - 2.2.6. Quantum Tunneling of the Magnetization 43
  - 2.3. Magnetic Interactions 46
    - 2.3.2. Exchange Interactions 48
    - 2.3.1. Zeeman Interaction 48
    - 2.3.4. Hyperfine Interactions 50
    - 2.3.3. Dipolar Interactions 50
    - 2.3.5. Single-Chain Magnets 51
  - 2.4. Beyond the Anisotropy Barrier: Energy Spectrum and Relaxation Times 53
  - 2.5. Summary 55
- 3. Computational Tools and Theoretical Methods 57
  - 3.2. Electrostatic Models 57
    - 3.2.1. “Electron Density” Electrostatic Model 58
    - 3.2.2. The Radial Effective Charge and the Lone-Pair Effective Charge Models 61
  - 3.1. Introduction 57
  - 3.3. Quantum Chemistry Methods 63
    - 3.3.1. Relativity in Quantum Chemistry 63
    - 3.3.2. Nonrelativistic Quantum Chemistry and Electron Correlation 65
  - 3.4. CASSCF-CASPT2/RASSI-SO Method 67
    - 3.4.1. Computational Data Analysis 68
      - 3.4.1.1. g-Tensor 69
      - 3.4.1.2. Transition Magnetic Moments 71
      - 3.4.1.3. Electron and Magnetization Spin Densities 75
      - 3.4.1.4. Magnetic Interactions 77
    - 3.4.2. Validity of the CASSCF-CASPT2/RASSI-SO Method 79
  - 4. Experimental Methods for Investigation of Relaxation Mechanisms in Lanthanide Molecular Magnets 82
    - 4.1. Introduction 82
    - 4.2. DC Magnetization and AC Susceptibility Experiments 83
      - 4.2.1. DC Magnetization 83
      - 4.2.2. Frequency Domain Measurements: Magnetic Relaxation 88
      - 4.2.3. Sub-Kelvin Temperature Measurements 94
    - 4.3. Heat Capacity Measurements 98
      - 4.3.1. Heat Capacity Contributions 98
      - 4.3.2. HC Measurement Methods 101
      - 4.3.3. Examples of HC Studies on Ln-Based SMMs 102
        
        4.3.3.2. Observation of Magnetic Ordering 103
        
        4.3.3.1. Determination of CF Splitting 103
        
        4.3.3.3. Determination of Magnetic Interactions 104
        
        4.3.3.4. Hyperfine Interaction 105
      - 4.4. Spectroscopic Methods 106
        
        4.4.1. Optical Absorption and Emission Spectroscopy 106
        
        4.4.2. FIR Spectroscopy 114
        
        4.4.3. Electron Paramagnetic Resonance 114
        
        4.4.4. Mössbauer Spectroscopy 117
        
        4.4.5. X-Ray Magnetic Circular Dichroism 118
        
        4.4.6. Inelastic Neutron Scattering 121
      - 4.5. Conclusions 123
    - 5. Lanthanide-Based SIMs 123
      - 5.1. Introduction 123
      - 5.2. Influence of the Lanthanide Ion 125
        
        5.2.1. Electron Density Distribution (Prolate vs Oblate) 125
        
        5.2.2. Kramers vs Non-Kramers Ions 135
        
        5.2.3. SIMs Based on Atypical Lanthanide Ions 136
        
        5.2.3.2. Gd(III) Ions 137
        
        5.2.3.1. Light Ln(III) Ions 137
        
        5.2.3.3. Heavy Ln(III) Ions 138
        
        5.2.3.4. Divalent Ln(II) Complexes 138
        
        5.3. Crystal Field Environment 139
        
        5.3.1. Symmetry 139
        
        5.3.1.2. Complexes Using Cyclic Ligands With High Rotational Symmetry 140
        
        5.3.1.2.1. C8-Symmetric Cyclooctatetraene (COT) Ligands 140
        
        5.3.1.1. Square-Antiprismatic D4d Symmetry Complexes 140
        
        5.3.1.1.3. POM-Based Complexes 140
        
        5.3.1.1.1. Sandwich-Type LnPc2 Complexes 140
        
        5.3.1.1.2. β-Diketonate DyIII Derivatives 140
        
        5.3.1.3. Complexes With Pentagonal-Bipyramidal D5h Symmetry 143
        
        5.3.2. Low Symmetry, Highly Axial CF 146
        
        5.3.4. Coordination Number 148
        
        5.3.3. Lanthanide-Radical SIMs 148
        
        5.3.5. Coordination Environment 150
        
        5.3.5.1. Second Coordination Environment 150
        
        5.3.5.1.1. Auxiliary Ligands 153
        
        5.3.5.1.2. Second Coordination Sphere 156
        
        5.3.6. Relaxation Through High States 156
        
        5.4. Conclusions and Outlook 159
        
        6. Dinuclear Lanthanide-Based SMMs 161
        
        6.1. Homo Dinuclear [Ln2] SMMs 161
        
        6.1.1. Dinuclear 4f Clusters With New Ln-Ln Bridges 161
        
        6.1.1.1. Oxygen-Based Bridges (Table 5) 161
        
        6.1.1.2. Carboxylic Bridges (Table 6) 167
        
        6.1.1.3. Nitrogen-Based Bridges (Table 6) 170
        
        6.1.1.4. C-aromatic Bridges (Table 6) 171
        
        6.1.1.5. Radical Bridges 171
        
        6.1.2. Influence of the Intradimer Coupling on Magnetic Relaxation 174
        
        6.2. Heterodinuclear SMMs 185
        
        6.2.1. [Ln-Ln'] Complexes 185
        
        6.2.2. Hetero [Ln-3d] Complexes 187
        
        6.3. Conclusions 189
        
        7. Polynuclear Lanthanide-Based SMMs 190
        
        7.1. Introduction 190
        
        7.2. Homonuclear Ln Clusters (Lnx', x>2): SMTs and SMMs 190
        
        7.2.1. Dy3 Triangles 197
        
        7.2.2. Tetranuclear Dy SMMs and SMTs 198
        
        7.2.3. Hexanuclear Dy SMMs 201
        
        7.2.4. High Nuclearity Ln SMMs 203
        
        7.2.5. New Synthetic Strategies 203
        
        7.3. Heteronuclear Ln-3d Clusters 204
        
        7.3.1. Heteronuclear Trimers 206
        
        7.3.2. Heteronuclear Tetrameric Clusters 206
        
        7.3.3. Clusters with Higher Nuclearity 216
        
        7.4. Conclusions 216
        
        8. 1D, 2D, and 3D Extended Systems 218
        
        8.1. 1D Molecular Magnets 219
        
        8.1.1. Polymers With SIM Behavior 219
        
        8.1.2. Crossover From SIM to Collective Fluctuations 225
        
        8.1.3. Single-Chain Magnets 227
        
        8.1.4. 1D Cluster Compounds 232
        
        8.2. Higher Dimensionality 237
        
        8.2.1. 2D Compounds 237
        
        8.2.2. 3D Compounds 245
        
        8.3. Conclusions 248
        
        9. Molecular Magnets on Surfaces 248
        
        9.1. Selected Molecular Systems 254
        
        9.2. Experimental Techniques 255
        
        9.3. Surfaces and Substrates 257
        
        9.3.1. Nonmagnetic Metals 257
        
        9.3.2. Magnetic Substrates 259
        
        9.3.3. Nonmetallic Substrates 260
        
        9.3.4. Carbon Substrates 261
        
        9.4. Devices 262
        
        9.4.1. TbPc2 Spintronics 262
        
        9.4.2. Cooling Devices 266
        
        9.5. Conclusions and Outlook 267
        
        10. Conclusions and Perspectives 268
        
        Acknowledgments 273
        
        References 273
      - Chapter 2: Laser-Induced Ultrafast Magnetic Phenomena 313
        
        1. Introduction 314
        
        2. Theoretical Approaches to Describe Laser-Induced Magnetization Dynamics 319
        
        2.1. Phenomenological Description of Laser-Driven Spin Dynamics 320
        
        2.2. Derivation of Relativistic Effects 322
        
        2.3. Interaction Between Light and Magnetic Medium 326
        
        2.3.1. Interaction With Circularly Polarized Light 329
        
        2.4. Magnetization Dynamics in the Ultrafast Range 332
        
        2.4.1. Dynamic Equations for Atomic Magnetic Moments 333
        
        2.4.2. Dynamic Equations for the Macroscopic Magnetization 338
        
        2.4.3. Spin-Flip Processes 341
        
        2.4.4. Spin Transport of Hot Electrons 342
        
        2.5. Ab Initio Methods for Calculating Exchange Interactions, Magneto-Optical Response, and Scattering Processes 345
        
        2.5.1. MO Response of a Sample With Excited Electrons 347
        
        2.5.2. Exchange Interactions and Finite Temperature Effects 349
        
        2.5.3. Phonon-Induced Spin-Flips 351
        
        2.5.4. Magnons and Electron-Magnon Scattering 355
        
        3. Experimental Methods to Study Laser-Induced Magnetization Dynamics 360
        
        3.1. All-Optical Detection Techniques 361
        
        3.1.1. Linear Magneto-Optics 361
        
        3.1.2. Nonlinear Magneto-Optics 364
        
        3.2. Time-Resolved Magneto-Optical Spectroscopy 366
        
        3.3. Time-, Energy-, Momentum-, and Spin-Resolved Electron Spectroscopy 368
        
        3.4. Time-, Spatial-, and Element-Resolved X-Ray Measurements of Spin Dynamics 371
        
        3.4.1. Ultrafast Magnetism and X-Rays 371
        
        3.4.2. Soft X-Rays vs XUV Probing 373
        
        3.5. Time-Resolved THz-Based Studies 375
        
        3.5.1. THz Spectroscopy 375
        
        3.5.2. THz Pumping 377
        
        4. Ultrafast Demagnetization 378
        
        4.1. Demagnetization in Transition Metals and Their Compounds or Alloys 378
        
        4.2. Demagnetization in Rare-Earth Based Materials 383
        
        4.3. Demagnetization in Half-Metals, Semiconductors, or Insulators 387
        
        4.4. Discussion of the Relation Between the Observed MO Response and Magnetization 391
        
        4.5. Character of the Demagnetized State 394
        
        5. Ultrafast Magnetization Switching 400
        
        5.1. Early Work on Magnetization Switching 401
        
        5.1.1. Thermal- and Magnetic-Field Assisted Magnetization Switching: Thermomagnetic Recording 401
        
        5.1.2. Coherent Precessional Switching 402
        
        5.2. Overview of Laser-Induced Magnetization Switching 405
        
        5.2.1. All-Optical Magnetization Switching in GdFe Alloys 405
        
        5.2.2. Helicity Independent (Toggle) Magnetization Switching 410
        
        5.2.3. Other Ferrimagnets 413
        
        5.2.4. Magnetization Switching in Ferromagnets 414
        
        5.2.5. Magnetization Switching in Ferrimagnetic Dielectrics 415
        
        5.3. Models of Heat-Driven Multisublattice Reversal 416
        
        5.3.1. Atomistic Spin Dynamics Simulation 416
        
        5.3.2. Orbital-Resolved Atomistic Spin Dynamics Simulation 418
        
        5.3.3. Simulations for Macroscopic Sublattice Magnetizations 420
        
        5.4. Inverse Faraday Effect 420
        
        6. Ultrafast Generation of Spin Currents 424
        
        6.1. Superdiffusive Model and Hot Electron Transport 429
        
        6.2. Thermally Driven Spin Currents 429
        
        6.3. Noncollinear Arrangement and Spin Torques 432
        
        7. Discussion of Underlying Physical Mechanisms 438
        
        7.1. Different Scattering Mechanisms 438
        
        7.1.1. Direct Light-Spin Coupling 438
        
        7.1.2. Electron-Phonon Coupling 439
        
        7.1.3. Electron-Phonon Coupling With Dynamical Exchange 445
        
        7.1.4. Electron-Magnon Coupling 446
        
        7.1.5. Electron-Electron Scattering 447
        
        7.1.6. Spin-Lattice Coupling via Orbital Momentum 448
        
        7.1.7. Combination of Electron-Phonon and Electron-Magnon Scattering 450
        
        7.1.8. Impurity Scattering 450
        
        7.2. Spin Transport 450
        
        8. Concluding Remarks and Outlook 453
        
        References 456
        
        Acknowledgments 456
        
        Author Index 487
        
        Subject Index 521
        
        Material Index 527
        
        Back Cover 531

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