Metallic Magnetism

ISBN-13: 9783642500701 / Angielski / Miękka / 2012 / 232 str.

Herbert Capellmann

Opis

The magnetism of iron and other transition metals had been a subject of inten- sive research for a long time, but the understanding of the microscopic origin of "metallic magnetism" was quite limited until the early 1970's. During the last 10 to 15 years both theory and experiment contributed towards signif- icant progress in this field, such that today a qualitative understanding has been achieved. The word "qualitative" indicates that the knowledge is still not complete; although many properties, the ground state as well as the finite- temperature behaviour and the phase transition from magnetic order at low temperatures to the paramagnetic state at high temperatures, can be explained in a coherent way, a quantitative description still is not fully achieved. It is certainly appropriate to summarize the developments of the last 15 years and the present-day understanding of the field, this is the aim of this Topics volume. The form chosen is a collection of reviews, written by prominent scientists who themselves contributed decisively to the progress. Scientists with a general interest in the field as well as specialists and active researchers in metallic magnetism should be able to profit from the two-volume treatment. The subjects not covered extensively in the present first volume (in particular neutron scattering and electronic structure properties) will make up the second volume.

Spis treści

1. Introduction.- 1.1 Preliminary Remarks.- 1.2 Ground State and Elementary Excitations.- 1.3 Finite Temperature Properties: What Drives the Phase Transition?.- 1.3.1 The Temperature Dependence of ?.- 1.3.2 Amplitude Fluctuations.- 1.3.3 Transverse Fluctuations.- 1.4 The Paramagnetic Phase.- 1.5 Organization of the Book.- References.- 2. A Unified Picture of Magnetism.- 2.1 Background.- 2.1.1 Historical Development.- 2.1.2 Outline.- 2.2 Theory of Magnetism Based on the Band Model.- 2.2.1 The Ground State.- 2.2.2 Magnetic Excitations from the Ground State.- 2.2.3 Finite-Temperature Properties.- 2.3 Self-Consistent Renormalization Theory for the Coupled Extended Modes of Spin Fluctuations.- 2.3.1 General Discussion.- 2.3.2 Theory Above TC.- 2.3.3 Theory Below TC.- 2.3.4 Comparison with Experiment.- 2.3.5 Supplementary Discussions on the SCR Theory.- 2.4 A Unified Description of Magnetism — Adiabatic Approximation.- 2.4.1 General Considerations.- 2.4.2 Functional Integral Theory.- 2.4.3 Mean Mode-Mode Coupling Theory of Spin Fluctuations — An Interpolation Theory.- 2.4.4 Physical Properties in the Intermediate Regime.- 2.4.5 Supplementary Discussions.- 2.5 Dynamical Properties of Spin Fluctuations.- 2.5.1 General Remarks.- 2.5.2 Spin Waves at Low Temperatures.- 2.5.3 Spin Correlations Above TC.- 2.5.4 Limitations of the Static Approximation.- 2.5.5 Present Status and Future Prospect of the Theory.- 2.6 Conclusion.- References.- 3. 3d-Metallic Magnetism and Spin-Resolved Photoemission.- 3.1 Background.- 3.2 The Electronic Structure of Ferromagnets.- 3.2.1 Low-Temperature Properties (Band Model).- 3.2.2 Models for 3d-Metallic Magnetism at Finite Temperatures.- 3.3 Concepts of Spin- and Angle-Resolved Photoemission from Ferromagnets.- 3.3.1 Models for the Photoemission Process.- 3.3.2 Experimental Methods to Test the Band Structure.- 3.3.3 Description of Spin Polarized Electrons.- 3.3.4 Surface Sensitivity.- 3.4 Apparatus for Spin- and Angle-Resolved Photoemission.- 3.4.1 Ferromagnetic Samples and Their Preparation.- 3.4.2 Light Sources and Electron Spectrometers.- 3.4.3 Spin Detection.- 3.5 The Electronic Structure of Ni and Fe at Low Temperatures.- 3.5.1 Photothreshold Experiments.- 3.5.2 Spin- and Angle-Resolved Photoemission at Low Temperatures.- 3.6 Resonant Photoemission and Auger Electrons.- 3.7 Secondary Electron Spin Polarization and Stoner Excitations.- 3.8 Finite Temperature Ferromagnetism and Photoemission.- 3.8.1 A Simple Model.- 3.8.2 Experimental Results for Fe and Ni and Their Interpretation.- 3.8.3 Photoemission from Ni.- 3.9 Concluding Remarks and Outlook.- References.- 4. The Local-Band Theory.- 4.1 Background.- 4.1.1 General Considerations.- 4.1.2 Green’s Function Structure.- 4.1.3 Functional Integrals.- 4.2 Single-Particle States and Energies.- 4.2.1 The Rotated Reference Frame.- 4.2.2 Perturbation Theory.- 4.2.3 Discussion.- 4.3 Green’s Functions.- 4.3.1 Formal Analysis.- 4.3.2 Limiting Cases.- 4.3.3 Fermi-Liquid Theory.- 4.3.4 Green’s Function Moments.- 4.4 Green’s Functions Revisited: The Rotated Frame.- 4.4.1 Formal Analysis.- 4.4.2 Approximate Evaluation.- 4.4.3 Zero-Point Effects.- 4.5 Model Analysis.- 4.5.1 Temperature-Dependent Parameters.- 4.5.2 Model Nickel Spectra.- 4.5.3 Iron Results.- 4.6 Conclusion.- 4. A Appendix.- References.- 5. Electron Correlations in Transition Metals.- 5.1 Background.- 5.2 The Correlated Ground State.- 5.2.1 Physical Interpretation of Electron Correlations.- 5.2.2 Density Functional Method.- 5.2.3 Correlated Ground State Wave Function.- 5.3 Correlation Effects in Single-Particle Excitations.- 5.4 Finite Temperature Calculations.- 5.4.1 Static Approximation.- 5.4.2 Beyond the Static Approximation.- 5.5 Influence of Correlations on the Photoelectron Spectra from Inner-Core States.- References.- 6. Magnetovolume Effects.- 6.1 Physical Mechanisms.- 6.1.1 Non-Magnetic Effects.- 6.1.2 Crystal Field Effects.- 6.1.3 Local Moment Interactions.- 6.1.4 Band Mechanism.- 6.1.5 Temperature Dependence.- 6.2 Experimental Results.- 6.2.1 Properties of the d Series at Fixed Temperature.- 6.2.2 Temperature Dependence — Weakly Magnetic Systems.- 6.2.3 Thermal Variation — Systems with Strong Moments.- 6.2.4 Compounds.- 6.2.5 Heusler Alloys.- 6.2.6 Amorphous Ferromagnets.- 6.2.7 Spin Glasses.- 6.2.8 Mn Alloys.- 6.2.9 Frequency Dependence of Elastic Moduli.- 6.2.10 Intermediate Valence Systems.- References.- Additional References with Titles.