Handbook of Magnetic Materials (eBook)

Cover 1
Contents 10
Preface to Volume 16 6
Contents of Volumes 1–15 12
List of Contributors 16
Giant Magnetostrictive Materials 18
Introduction 20
Magnetic shape memory effect 21
Selected active materials 21
Modelling the behaviour of MSM materials and the giant magnetic-field-induced strain (MFIS) 22
Ni-Mn-Ga alloys 24
Martensitic and reverse phase transformations 24
Mechanical properties 25
Magnetic properties 29
Martensite variant rearrangement in an applied magnetic field 33
Effect of load on magnetic-field-induced strain (MFIS) 35
Dynamical actuation and fatigue of MFIS 36
Temperature dependence of MFIS 38
Selected properties of Ni-Mn-Ga alloys 39
Promising MSM materials 40
Acknowledgements 41
References 42
Micromagnetic Simulation of Magnetic Materials 58
Introduction 60
Basic micromagnetism 62
Total Gibbs' energy 62
Exchange energy 63
Ferromagnet 63
Ferrimagnets and antiferromagnets 63
Antiferromagnetic ordering on a simple cubic lattice 63
Antiferromagnetic ordering on a body-centered cubic lattice 66
Antiferromagnetic ordering on an fcc lattice 66
Zeeman energy 67
Magnetocrystalline anisotropy energy 67
Magnetic field 68
Interface condition 69
Strayfield 69
Eddy current field 71
Static micromagnetism-Browns equation 72
Dynamic micromagnetics 73
Micromagnetism at finite temperature 75
Short time scales-stochastic dynamics 75
Long time scales-energy barriers 76
Numerical methods 78
Finite difference micromagnetism 79
Finite element micromagnetism 81
Numerical treatment of the stray field problem 84
Vector potential 85
Scalar potential 85
Hybrid FE/BE method 86
Finite element method-Galerkin approach 88
Eddy currents 90
Model 90
Fast integration methods 91
Fast Fourier transformation 91
Treecode 93
H-matrices-adaptive cross approximation 94
Time integration 96
Time discretization 98
Comparison of different time integration schemes 99
Time integration at finite temperature 101
Calculating energy barriers 103
Micromagnetic codes 105
Applied micromagnetics 108
Perpendicular and tilted media for magnetic recording 108
Reversal modes 109
Energy barriers and thermally activated reversal modes 110
Switching times 113
Single domain particle 115
Granular media 119
Conclusions 121
Exchange spring media for perpendicular recording 122
Analytical model for single phase media 123
Numerical results for single phase media and exchange spring media 124
Conclusion 128
Integrated simulations of recording devices 128
Numerical background 129
Longitudinal recording 129
Perpendicular recording 130
Conclusion 134
Acknowledgement 134
References 139
Ferrofluids 144
Synthesis of magnetic fluids 147
Stability criteria 147
Magnetite ferrofluids 151
Ferrofluids containing metallic particles 154
Ferrofluids for biomedical applications 155
Basic properties of ferrofluids 155
Magnetic properties 156
Equilibrium magnetization 156
Relaxation of magnetization 160
Viscous properties 163
Basic description for the field dependent behaviour of ferrofluids 164
Basic ferrohydrodynamic equations 165
An overview on applications of magnetic fluids 168
Sealing applications 168
Ferrofluids for separation purposes 170
Ferrofluids for sensor applications 171
Ferrofluids as heat transfer medium 172
Ferrofluids for positioning applications 173
Magnetic control of fluid properties and fluid flow 174
Field dependent viscous properties of ferrofluids 174
The magnetoviscous effect 174
The magnetoviscous effect in diluted ferrofluids 177
Negative viscosity 179
Magnetoviscous effects in concentrated ferrofluids 181
The rheological behaviour of ferrofluids 183
Microscopic models for the magnetoviscous behaviour 189
Consequences of the microstructural picture for the magnetoviscous effects 201
Thermal transport properties 208
The Soret effect in ferrofluids 208
Thermal convection in ferrofluids 212
Medical applications of ferrofluids 220
References 222
Magnetic and Electrical Properties of Practical Antiferromagnetic Mn Alloys 226
Main list of abbreviations and symbols 229
Introduction 232
Morphologies of Mn 233
Electronic and magnetic structures of Mn alloys 235
Model for the itinerant electron system 236
Minimal models of itinerant electron magnetism 237
Path-integral approach for itinerant electron magnetism 239
Saddle point (molecular filed) approximation 241
Helical magnetic structures 243
Rotation of local spin axes for the complex magnetic structures 248
Magnetic excitation energies and the exchange constants 251
First principles approach for the magnetic structures of transition metal systems 258
Tight-binding (TB)-LMTO method for the complex magnetic structures 259
Coherent potential approximation (CPA) for disordered alloys 262
Effective exchange constant 263
Electronic and magnetic structures of gamma-Mn, L12-type ( gamma'-phase) and L10-type alloys 263
Pure gamma-Mn 264
Magnetic structure of pure gamma-Mn 264
Exchange constant of pure gamma-Mn 267
L12-type (gamma'-phase) ordered and gamma-phase disordered Mn3Ir and Mn3Rh alloys 268
L10-type ordered MnRh, MnIr, MnPt, MnPd and MnNi alloys 273
Comparison between the ordered and disordered phases of equiatomic MnPt alloys 278
Stability of B2 phase of MnRh equiatomic alloy 282
Experimental observations of antiferromagnetic transition and magnetic moments of Mn alloys 284
The Néel temperature and the magnetic moment of L12-type (gamma'-phase) ordered (O) alloy systems 284
The Néel temperature and the magnetic moment of gamma-phase disordered (DO) alloy systems 286
Magnetic structures of L12-type (gamma'-phase) Mn3Pt and Mn3Ir ordered (O) alloy systems 290
D- and F-phases of L12-type (gamma'-phase) ordered Mn3Pt 290
Magnetic reflection of L12-type (gamma'-phase) ordered Mn3Ir 295
Crystallographic phase transformation between B2 and L10-type phase 296
The Néel temperature of L10-type alloy systems 297
Strong bonding state correlated with magnetic moment and Pauling valence 301
Volume contraction of L10-type alloy systems 301
Relation between magnetic moment and Pauling valence 303
Fundamental properties of practical Mn alloys 305
Low-temperature specific heat 305
L12-type (gamma'-phase) ordered and gamma-phase disordered alloys 306
L10-type alloys 307
Electrical resistivity 309
L12-type (gamma'-phase) ordered and gamma-phase disordered alloy systems 309
L10-type alloy systems 313
Spin valves 317
Reflectivity and thermoelectric power of L10-type MnPt alloys 319
Magnetic anisotropy in gamma-phase disordered alloys and L10-type ordered alloys 321
Magnetic anisotropy in gamma-phase disordered alloys 321
Magnetic anisotropy in L10-type alloys 325
Spin structures and lattice distortions of gamma-phase disordered alloys 327
Spin structure and magnetic susceptibility 328
Phase diagram and lattice distortion of Mn-Rh, Mn-Ga and Mn-Ru alloy systems 330
Phase diagram and spin structures of Mn-Ir alloy system 333
Appearance of the beta-phase and stabilization of the gamma-phase 337
Spin fluctuation effects in beta-Mn alloys 342
Concentration and temperature dependences of magnetic properties of the L10-type alloy systems 345
Magnetic moment and the Néel temperature of MnPt and MnPd alloy systems 345
Temperature dependence of the magnetic susceptibility and magnetic cooling effect 346
Magnetic phase diagram and spin structures 348
Magnetovolume effects and elastic properties of Mn alloys 357
L12-type (gamma'-phase) ordered and gamma-phase disordered alloys 358
beta-Mn alloys 362
L10-type alloys 363
Compressibility and bulk modulus of Mn alloys 364
Mechanism of exchange bias-field in spin valves 370
Survey proposed models of exchange coupling bias 371
Single spin model 371
Antiferromagnetic (AFM) domain wall model 372
Random-field model 373
Domain state model 374
Spin flop model 375
Defect models 375
Analytical models 377
Polycrystalline models 378
Other models 379
Main problems in the proposed models 380
Generalized model based on classical Heisenberg model 382
Total magnetic energy and equation of motion 382
Unidirectional exchange bias-field 384
Formation of magnetic domain wall in antiferromagnetic layer 388
Magnetic domain wall in 3Q spin structure 388
Introduction of multi-domains into L10-type antiferromagnetic layer 390
Cubic anisotropy and torque curves 394
Cubic anisotropy and exchange bias-field 395
Torque curves of FM/AFM bilayer 398
Appearance of 2Q in 3Q spin structure 402
Uncompensated spin element in AFM layer at the interface 403
Blocking temperature and training effect 405
Blocking temperature 405
Training effect 407
Concluding remarks 409
Acknowledgements 411
References 411
Synthesis, Properties and Biomedical Applications of Magnetic Nanoparticles 420
Introduction 422
Synthesis of magnetic nanoparticles 426
Solution routes 427
Precipitation from homogenous solutions 428
Precipitation from aqueous solutions 428
Precipitation from organic solutions 430
Organic reactors 436
Organized surfactant assemblies 436
Other organic and biological reactors 438
Liquid aerosols 442
Other solution routes 442
Gas-phase routes 444
Solid routes 445
Size selection methods 447
Colloidal properties of magnetic nanoparticles 447
Surface modification or encapsulation of nanoparticles 452
Organic hydrophilic coatings 452
Polysaccharides 453
Synthetic polymers 456
Encapsulation in liposomes and artificial capsules 458
Inorganic hydrophilic coatings 459
Hybrid hydrophilic coatings 463
Hydrophobic coatings 464
Transformation of hydrophobic into hydrophilic particles 465
Magnetic properties of nanoparticles 465
Particle size effects (finite size and/or surface effects) 467
Other microstructural effects 470
Coating and encapsulation effects 471
Interparticle spacing 471
Surface modification 472
Applications of magnetic nanoparticles in biomedicine 475
Nuclear magnetic resonance (NMR) imaging 476
Hyperthermia 480
Magnetic drug-targeting and gene delivery 481
Separation and selection 484
Other biomedical applications of magnetic nanoparticles 487
Acknowledgements 488
References 488
Author Index 500
Subject Index 546
Materials Index 550