1. Introduction 2. Mean-Field Theory of Itinerant Electron Magnetism 3. Dynamical Mean-Field Theory of Spin Fluctuations 4. Self-Consistent Renormalization (SCR) Theory of Spin Fluctuations 5. Physical Properties of Weakly and Nearly Ferro- and Antiferromagnetic Metals 6. Local Magnetic Moments 7. A Unified Theory and Its General Consequences 8. Functional Integral Theory 9. Spin Fluctuations in d-Electron Systems 10. Toward a Unified Theory of Dynamical Spin Fluctuations

Ferromagnetism of metallic systems, especially those including transition metals, has been a controversial subject of modern science for a long time. This controversy sterns from the apparent dual character of the d-electrons responsible for magnetism in transition metals, i.e., they are itinerant elec trons described by band theory in their ground state, while at finite tem peratures they show various properties that have long been attributed to a system consisting of local magnetic moments. The most familiar example of these properties is the Curie-Weiss law of magnetic susceptibility obeyed by almost all ferromagnets above their Curie temperatures. At first the problem seemed to be centered around whether the d-elec trons themselves are localized or itinerant. This question was settled in the 1950s and early 1960s by various experimental investigations, in particular by observations of d-electron Fermi surfaces in ferromagnetic transition metals. These observations are generally consistent with the results of band calculations. Theoretical investigations since then have concentrated on explaining this dual character of d-electron systems, taking account of the effects of electron-electron correlations in the itinerant electron model. The problem in physical terms is to study the spin density fluctuati·ons, which are ne glected in the mean-field or one-electron theory, and their influence on the physical properties