Magnetism and structure in functional materials

Antoni Planes, Lluís Mañosa, Arvadh Saxena3540236724, 9783540316312, 9783540236726

Magnetism and Structure in Functional Materials addresses three distinct but related topics: (i) magnetoelastic materials such as magnetic martensites and magnetic shape memory alloys, (ii) the magnetocaloric effect related to magnetostructural transitions, and (iii) colossal magnetoresistance (CMR) and related magnanites. The goal is to identify common underlying principles in these classes of materials that are relevant for optimizing various functionalities. The emergence of apparently different magnetic/structural phenomena in disparate classes of materials clearly points to a need for common concepts in order to achieve a broader understanding of the interplay between magnetism and structure in this general class of new functional materials exhibiting ever more complex microstructure and function. The topic is interdisciplinary in nature and the contributors correspondingly include physicists, materials scientists and engineers. Likewise the book will appeal to scientists from all these areas.

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Table of contents :
Contents……Page 9
1 Complex Functional Materials……Page 17
2.1 Introduction……Page 19
2.2 Order Parameters and Multiferroics……Page 21
2.3.1 Levels of Description……Page 22
2.3.2 Definition of Unit-Cell Strain Tensor……Page 23
2.3.3 Strain Free Energy……Page 24
2.3.4 St Venant Compatibility Constraints……Page 25
2.3.5 Compatibility Potentials……Page 26
2.3.6 Other Approaches……Page 28
2.4 Inhomogeneities in Ferroelastics……Page 29
2.5 Inhomogeneities in Multiferroic Oxides……Page 32
2.6.1 Coupling of Variables……Page 34
2.6.2 Simulations……Page 35
2.7 Summary and Further Work……Page 37
References……Page 38
3.1 Introduction……Page 42
3.2 Disorder Distribution……Page 43
3.2.2 Premonitory Behaviour: Temperature Softening……Page 44
3.2.3 Structural Precursors……Page 46
3.2.4 Coupling to Magnetism……Page 48
3.2.5 Ferroic Precursors: Magnetic and Others……Page 50
3.3.1 Athermal Transitions……Page 52
3.3.3 Avalanche Dynamics……Page 55
3.3.4 Modelling Avalanches……Page 58
3.4 Conclusion……Page 60
References……Page 61
4.1 Introduction……Page 64
4.2.1 Gd[sub(5)](Si[sub(x)]Ge[sub(1–x)])[sub(4)]……Page 65
4.2.2 MnAs……Page 66
4.3.1 FeRh……Page 68
4.3.2 Hf[sub(1–x)]Ta[sub(x)]Fe[sub(2)]……Page 70
4.3.3 La(Fe[sub(x)]Al[sub(1–x)])[sub(13)]……Page 71
4.4 Metal–Insulator Transitions……Page 72
4.4.1 Colossal Magnetoresistance (CMR) and Huge Volume Effects……Page 74
4.4.2 Magnetostriction and Magnetoresistance in the Paramagnetic Phase……Page 76
4.4.3 Magnetostriction in Inhomogeneous Electronic Systems: Static Phase Segregation……Page 78
4.5 Charge/Orbital Instabilities……Page 80
4.6 Conclusion……Page 85
References……Page 86
5.1 Introduction……Page 89
5.2.1 Colossal Magnetoresistivity……Page 90
5.2.2 Pulsed Neutron PDF Method……Page 91
5.2.3 Polaron Stability……Page 93
5.3 Stability of Spin–Charge Stripes in the Cuprates……Page 97
5.4.2 Electron–Phonon Coupling in the Cuprates……Page 98
5.4.3 Vibronic Mechanism of High Temperature Superconductivity……Page 101
5.5 Conclusions……Page 103
References……Page 104
6.1 Introduction……Page 107
6.2 Neutron Scattering……Page 108
6.3 Phonon Anomalies……Page 109
6.3.1 Kohn Anomalies……Page 110
6.3.2 Soft Modes……Page 111
6.4 Phonon Anomalies in the Manganites……Page 113
6.5 Phonon Anomalies in High Temperature Superconductors……Page 114
6.6 Ferromagnetic Shape Memory Alloys……Page 116
6.6.1 Iron-Based Alloys……Page 117
6.6.2 Heusler-Based Alloys……Page 118
6.7 Summary……Page 124
References……Page 125
7.2 The Crystal Structure of the Cubic Austenite Phase……Page 127
7.3 Bulk Magnetic Properties……Page 130
7.5 Paramagnetic Response……Page 132
7.6 Inelastic Neutron Scattering……Page 133
7.7 Neutron Diffraction……Page 135
7.8 Pre-Martensitic Phase……Page 136
7.8.1 Field Dependence……Page 139
7.9 The Martensitic Phase……Page 140
7.10 Structural and Magnetic Phase Diagram……Page 141
7.11 Mechanism……Page 143
7.12 Martensitic Twinning in Ni[sub(2)]MnGa……Page 144
7.13 Non-Stoichiometric Samples……Page 147
7.14 Electron Concentration……Page 149
7.15 Polarised Neutron Scattering……Page 150
7.16 Conclusion……Page 151
References……Page 152
8.2.1 Classical Description……Page 155
8.2.2 Quantum Mechanical Description……Page 157
8.2.3 Phase Reconstruction……Page 159
8.3 Applications of LTEM to Ferromagnetic Shape Memory Alloys……Page 162
8.3.1 Ni[sub(2)]MnGa, Austenitic State……Page 163
8.3.2 Ni[sub(2)]MnGa, Martensitic State……Page 166
8.3.3 Co[sub(2)]NiGa, Austenitic State……Page 167
8.3.4 Co[sub(2)]NiGa, Martensitic State……Page 168
References……Page 170
9.1 Introduction……Page 172
9.3 Basic Idea……Page 173
9.4 Lattice Parameter Sensitivity……Page 174
9.5 What Makes Big First Order Phase Transformations Reversible?……Page 175
9.6 Specific Relationships Among Lattice Parameters for a High Degree of Reversibility……Page 182
9.6.2 Cubic to Monoclinic Transformations……Page 183
9.7 Tuning Lattice Parameters to Satisfy Two of the Proposed Conditions in the NiTiCuPd System……Page 184
9.8 Further Comparisons with Experiment……Page 185
References……Page 187
10.2 Invar……Page 189
10.3 From Invar to Anti-Invar……Page 193
10.4 Allotropy of Pure Fe……Page 196
10.5 Ground State Properties of Invar and Anti-Invar……Page 199
10.6 Pressure Experiments: Evidence for High Spin to Low Spin State Transitions……Page 201
10.7 HS–LS Transitions in a Microscopic Picture……Page 204
10.8 Questions and Outlook……Page 207
References……Page 208
11.2 Magnetic Cooling or Why Having a Strong Magnetocaloric Effect in a Weak Magnetic Field Makes a Difference?……Page 210
11.3 Gd[sub(5)](Si[sub(4–x)]Ge[sub(x)]) System and the Giant Magnetocaloric Effect……Page 213
11.4 Altering Crystal Structures with a Magnetic Field……Page 217
11.5 To What Extent a Structural Change Enhances the Giant Magnetocaloric Effect?……Page 225
11.6 Conclusions……Page 230
References……Page 231
12.1 Introduction……Page 234
12.2 Multiscale Origin of the MCE in Ni–Mn–Ga Alloys……Page 236
12.3 Direct Determination of the Entropy Change at a First-Order Transformation……Page 240
12.4 Magnetostructural Transformation in Gd–Si–Ge Alloys……Page 241
References……Page 246
13 Functional Magneto-Structural Materials: Summary and Perspectives……Page 248
References……Page 254
D……Page 257
I……Page 258
P……Page 259
T……Page 260
Z……Page 261