SOME ASPECTS OF THE THEORY OF SPIN-GLASSES AND DISORDERED FERROMAGNETS

This review is concerned with some aspects of the theory of disordered magnets and spin glasses and is mainly based on results of the authors. The concept of spin glass is extended to the case of magnets with itinerant magnetic electrons (Stoner magnets). Different properties of disordered ferri- and ferromagnets and spin glasses (alloys of 3d- and 4f-metals, metallic glasses) are studied by means of percolation theory. The transition from the metastable to the stable ground state of a spin glass with anisotropy is discussed within the scope of the phenomenological theory. Some aspects of the spin glass behavior are described using the idea that a spin glass is a stochastic antiferromagnet. The spectra of magnetic excitations (magnetic rotons) are obtained for different types of disordered magnets.