Spin-wave theory and its applications to neutron scattering and THz spectroscopy
Spin waves Microwave spectroscopy Neutrons
IOP Publishing
2018
EISBN 9781643271149
1. Introduction.
2. Inelastic neutron scattering.
2.1. Introduction.
2.2. Neutron scattering basics.
2.3. Some practical considerations.
2.4. Instruments for INS.
2.5. Neutron scattering at large user facilities.
2.6. Exercises
3. THz spectroscopy.
3.1. Introduction.
3.2. THz spectroscopy in high magnetic fields.
3.3. Acquisition and analysis of single-crystal SW spectra.
3.4. Selection rules.
3.5. Summary.
3.6. Exercises
4. Spin-wave theory.
4.1. Introduction.
4.2. SW formalism.
4.3. Spin-spin correlation function and INS.
4.4. THz spectroscopy.
4.5. SW amplitudes.
4.6. General considerations.
4.7. Appendix 4.A : symmetry and matrices.
4.8. Appendix 4.B : classical check.
4.9. Appendix 4.C : shortcuts.
4.10. Appendix 4.D : orthogonal and hexagonal notations.
4.11. Appendix 4.E : spin susceptibility.
4.12. Exercises
5. Model collinear magnets.
5.1. Introduction.
5.2. A FM in a magnetic field.
5.3. A FM chain with alternating exchange interactions.
5.4. A FM on a honeycomb lattice.
5.5. An AF in a magnetic field.
5.6. Powder spectra.
5.7. Exercises
6. Model non-collinear magnets.
6.1. Introduction.
6.2. An AF chain with alternating DM interactions.
6.3. A helix or cycloid produced by CE.
6.4. A cycloid produced by DM interactions.
6.5. Comparison of CE and DM cycloids.
6.6. Incommensurate cycloids in 2D or 3D.
6.7. A helix produced by GF on a TLA.
6.8. The inverse problem.
6.9. Exercises
7. Inelastic neutron-scattering case studies.
7.1. Introduction.
7.2. Amorphous FMs.
7.3. An easy-axis AF.
7.4. A multiferroic metal-organic framework.
7.5. Spin states of a TLA.
7.6. Summary
8. THz spectroscopy case studies.
8.1. Introduction.
8.2. A cycloid produced by DM interactions.
8.3. An AF with strong easy-plane anisotropy.
8.4. Prospects for the future.
9. Conclusion.
Two of the most powerful tools used to study magnetic materials are inelastic neutron scattering and THz spectroscopy. Because the measured spectra provide a dynamical fingerprint of a magnetic material, those tools enable scientists to unravel the structure of complex magnetic states and to determine the microscopic interactions that produce them. This book discusses the experimental techniques of inelastic neutron scattering and THz spectroscopy and provides the theoretical tools required to analyze their measurements using spin-wave theory. For most materials, this analysis can resolve the microscopic magnetic interactions such as exchange, anisotropy, and Dzyalloshinskii-Moriya interactions. Assuming a background in elementary statistical mechanics and a familiarity with the quantized harmonic oscillator, this book presents a comprehensive review of spin-wave theory and its applications to both inelastic neutron scattering and THz spectroscopy. Spin-wave theory is used to study several model magnetic systems, including non-collinear magnets such as spirals and cycloids that are produced by geometric frustration, competing exchange interactions, or Dzyalloshinskii-Moirya interactions. Several case studies utilizing spin-wave theory to analyze inelastic neutron-scattering and THz spectroscopy measurements are presented. These include both single crystals and powders and both oxides and molecule-based magnets. In addition to sketching the numerical techniques used to fit dynamical spectra based on microscopic models, this book also contains over 70 exercises that can be performed by beginning graduate students.
2. Inelastic neutron scattering.
2.1. Introduction.
2.2. Neutron scattering basics.
2.3. Some practical considerations.
2.4. Instruments for INS.
2.5. Neutron scattering at large user facilities.
2.6. Exercises
3. THz spectroscopy.
3.1. Introduction.
3.2. THz spectroscopy in high magnetic fields.
3.3. Acquisition and analysis of single-crystal SW spectra.
3.4. Selection rules.
3.5. Summary.
3.6. Exercises
4. Spin-wave theory.
4.1. Introduction.
4.2. SW formalism.
4.3. Spin-spin correlation function and INS.
4.4. THz spectroscopy.
4.5. SW amplitudes.
4.6. General considerations.
4.7. Appendix 4.A : symmetry and matrices.
4.8. Appendix 4.B : classical check.
4.9. Appendix 4.C : shortcuts.
4.10. Appendix 4.D : orthogonal and hexagonal notations.
4.11. Appendix 4.E : spin susceptibility.
4.12. Exercises
5. Model collinear magnets.
5.1. Introduction.
5.2. A FM in a magnetic field.
5.3. A FM chain with alternating exchange interactions.
5.4. A FM on a honeycomb lattice.
5.5. An AF in a magnetic field.
5.6. Powder spectra.
5.7. Exercises
6. Model non-collinear magnets.
6.1. Introduction.
6.2. An AF chain with alternating DM interactions.
6.3. A helix or cycloid produced by CE.
6.4. A cycloid produced by DM interactions.
6.5. Comparison of CE and DM cycloids.
6.6. Incommensurate cycloids in 2D or 3D.
6.7. A helix produced by GF on a TLA.
6.8. The inverse problem.
6.9. Exercises
7. Inelastic neutron-scattering case studies.
7.1. Introduction.
7.2. Amorphous FMs.
7.3. An easy-axis AF.
7.4. A multiferroic metal-organic framework.
7.5. Spin states of a TLA.
7.6. Summary
8. THz spectroscopy case studies.
8.1. Introduction.
8.2. A cycloid produced by DM interactions.
8.3. An AF with strong easy-plane anisotropy.
8.4. Prospects for the future.
9. Conclusion.
Two of the most powerful tools used to study magnetic materials are inelastic neutron scattering and THz spectroscopy. Because the measured spectra provide a dynamical fingerprint of a magnetic material, those tools enable scientists to unravel the structure of complex magnetic states and to determine the microscopic interactions that produce them. This book discusses the experimental techniques of inelastic neutron scattering and THz spectroscopy and provides the theoretical tools required to analyze their measurements using spin-wave theory. For most materials, this analysis can resolve the microscopic magnetic interactions such as exchange, anisotropy, and Dzyalloshinskii-Moriya interactions. Assuming a background in elementary statistical mechanics and a familiarity with the quantized harmonic oscillator, this book presents a comprehensive review of spin-wave theory and its applications to both inelastic neutron scattering and THz spectroscopy. Spin-wave theory is used to study several model magnetic systems, including non-collinear magnets such as spirals and cycloids that are produced by geometric frustration, competing exchange interactions, or Dzyalloshinskii-Moirya interactions. Several case studies utilizing spin-wave theory to analyze inelastic neutron-scattering and THz spectroscopy measurements are presented. These include both single crystals and powders and both oxides and molecule-based magnets. In addition to sketching the numerical techniques used to fit dynamical spectra based on microscopic models, this book also contains over 70 exercises that can be performed by beginning graduate students.
