Magnetic crystals are ideal systems to study the universal properties of phase transitions, particularly systems with quenched randomness and frustration. Pure systems with different symmetries provide the foundation for studies in corresponding systems with quenched randomness. Because phenomena near phase transitions have universal properties, results from bulk magnetic crystals provide a basis for understanding phase transitions in films and nanoparticles, as well as many non-magnetic materials. This motivates the subject of this book, which discusses phase transitions studies in magnetic crystals from the perspective of an experimentalist who has done extensive work in the field. The advantage is that many experimental techniques are described in sufficient detail for a good understanding of the results and their comparison to theory.
Author(s): Daivd P. Belanger
Publisher: World Scientific Publishing
Year: 2022
Language: English
Pages: 245
City: Singapore
Contents
Preface
Acknowledgment
1. An Introduction to Phase Transitions and Universality
2. Universal Critical Behavior from Theory and Simulations
3. Background on Experimental Techniques
3.1 Thermometry
3.2 Specific Heat Techniques
3.3 Optical Measurements of Critical Behavior
3.3.1 Optical birefringence
3.3.2 Specific heat critical behavior via birefringence techniques
3.3.3 Faraday rotation
3.3.4 Isotropic magnets and the birefringence technique
3.4 Capacitance
3.5 Susceptibility and Thermal Expansion
3.6 Neutron and X-ray Scattering Measurements
3.6.1 Elastic scattering
3.6.2 Inelastic scattering
3.7 The Effect of Concentration Gradients on Critical Behavior Characterizations
4. Critical Behavior Experiments on Anisotropic and Isotropic Antiferomagnets
4.1 Crystals
4.1.1 d = 3 Anisotropic crystals
4.1.1.1 Crystal structure of FeF2, MnF2, and ZnF2 and magnetic interactions of FeF2 and MnF2
4.1.1.2 Crystal structure of FeCl2
4.1.2 d = 2 Anisotropic crystals
4.1.3 d = 3 Isotropic crystals
4.2 Phase Diagram Measurements of Anisotropic and Isotropic Antiferromagnets
4.2.1 The bicritical and tricritical points in pure and dilute anisotropic antiferromagnets
4.2.2 The influence of anisotropy on the transition TN
4.3 Specific Heat Critical Behavior of Pure Ising Antiferromagnets
4.3.1 d = 2 Pure Ising specific heat critical behavior
4.3.2 d = 3 Pure Ising specific heat critical behavior
4.4 The Order Parameter of Pure Ising Antiferromagnets
4.4.1 d = 2 Pure Ising order parameter
4.4.2 d = 3 Pure Ising order parameter
4.5 Neutron Scattering Critical Line Shapes of Pure Ising Antiferromagnets
4.5.1 d = 2 Pure Ising neutron scattering
4.5.2 d = 3 Pure Ising neutron scattering
4.6 The Random-Exchange Ising Model
4.6.1 d = 2 Random-exchange Ising model
4.6.2 d = 3 Random-exchange Ising order parameter
4.6.3 d = 3 Random-exchange Ising specific heat critical behavior
4.6.4 d = 3 Random-exchange neutron scattering
4.6.5 d = 3 Random-exchange dynamics
4.6.6 d = 3 Random-exchange susceptibility
4.7 The Random-Field Ising Model
4.7.1 d = 2 Random-field Ising critical behavior
4.7.2 d = 3 Random-field Ising critical behavior
4.7.3 d = 3 Random-field dynamics for x < xv
4.7.4 Vacancy percolation and the stability of d = 3 antiferromagnetic long-range order
4.7.5 d = 3 Random-field order parameter
4.7.6 d = 3 Random-field specific heat
4.7.7 d = 3 Random-field neutron scattering line shapes
4.8 d = 3 XY Specific Heat Critical Behavior
4.9 Experiments on Isotropic Magnets
4.9.1 Optical birefringence in isotropic antiferromagnets
4.9.2 The specific heat critical behavior of isotropic magnets
5. Domains, Excitations, and Spin-Glass-Like Behaviors
5.1 Domain Structure Dynamics at Low Temperature
5.2 The Phase Diagram of Anisotropic Antiferromagnets Above the Magnetic Percolation Threshold Concentration
5.3 Excitations Near the Magnetic Percolation Threshold Concentration
5.3.1 Fracton excitations in isotropic diluted d = 2 and d = 3 antiferromagnets near the magnetic percolation threshold concentration
5.3.2 Excitations in anisotropic d = 2 and d = 3 diluted antiferromagnets near the magnetic percolation threshold concentration
6. Experiments on Pure Magnets with Frustration
6.1 The XY Stacked Triangular Lattice
6.2 Examples of Other Chiral Systems
6.2.1 Holmium
6.2.2 VF2
6.3 Ising Stacked Triangular Lattice
7. The Unusual Magnetism of LaCoO3: A Thermally Excited Exchange Interaction and Ordering at Twin Interfaces
8. Conclusions and Outstanding Questions
8.1 Overall Summary of the Results of the Experiments
8.2 Some Open Questions About Equilibrium in the Random-Field Ising Model
8.3 Future Work
Bibliography
Index
