1 Introduction 1

2 History of Conventional Spin Wave Theory 9

2.1 Theoretical and Experimental Confusions 9

2.2 Problems with the Macroscopic Magnetization 17

3 Basic Issues of Renormalization Group(RG)Theory 25

3.1 Dynamics of Non Magnetic Solids 25

3.2 Dynamics of Ordered Magnets 47

4 Universality 53

4.1 Non-Magnetic Solids 53

4.2 Ordered Magnets 58

5 Microscopic Processes 69

6 Non-Relevant Magnons 75

7 Crossover Phenomena 93

7.1 Amplitude Crossover(AC) 93

7.2 Quantum State Crossover(QS) 104

7.3 Crossover Between Stable Fixed Points(SFP) 113

7.4 Symmetry Crossover(SC) 119

7.5 Dimensionality Crossover(DC) 124

8 Metastability of Universality Classes 129

9 Relevant and Non-Relevant Interactions 139

10 Temperature Dependence of the Magnon Excitation Spectra 159

11 Magnetic Heat Capacity 167

11.1 NonRelevant Magnetic Heat Capacity for T→0 167

11.2 Relevant Magnetic Heat Capacity for T→0 171

12 Experimental Verification of GSW Bosons 185

13 Magnets With and Without Magnon Gap(Goldstone Mode) 199

13.1 Isotropic Magnets with Half-Integer Spin(T2 Universality Class) 201

13.2 Isotropic Magnets with Integer Spin(T9/2 Universality Class) 204

13.3 Two-Dimensional Magnets with Half-Integer Spin (T3/2 Universality Class) 205

13.4 Two-Dimensional Magnets with Integer Spin(T2 Universality Class) 207

13.5 One-Dimensional Magnets with Half-Integer Spin(T5/2 Universality Class) 208

13.6 One-Dimensional Magnets with Integer Spin(T3 Universality Class) 209

13.7 Field Dependence of the Classical Magnon Spectrum 221

14 Microscopic Details:Spin Structure,Site Disorder,Two Order Parameters 223

15 The Critical Magnetic Behaviour 241

15.1 Isotropic 3D Magnets with Half-Integer Spin(T2 Universality Class) 247

15.2 Anisotropic 3D Magnets with Half-Integer Spin(T3/2 Universality Class) 269

15.3 Isotropic 3D Magnets with Integer Spin(T9/2 Universality Class) 271

15.4 Anisotropic 3D Magnets with Integer Spin(T2 Universality Class) 283

15.5 Amorphous Ferromagnets 283

15.6 Two-Dimensional Magnets 289

15.7 One-Dimensional Magnets 294

16 Thermal Lattice Expansion and Magnetostriction 309

16.1 Spontaneous Magnetostriction 310

16.2 Thermal Lattice Expansion of Non-Magnetic Solids 328

17 The Total Energy Content 335

18 Superconductivity 339

18.1 Superconducting Heat Capacity 342

18.2 Superconducting Excitation Gap 358

18.3 Problems with Landau's Order Parameter Concept 364

19 Conclusions 367

References 375

Index 389