Magnetism of amorphous transition metals and alloys

Abstract

Recent development in the magnetism of amorphous transition metals (TMs) and alloys is summarized from the theoretical point of view. The magnetism is shown to be characterized by the itinerant-electron spin glass and re-entrant spin-glass behaviors around amorphous Fe, the enhancement of Curie temperature around amorphous Co, and a weak ferromagnetism around amorphous Ni. The systematic change in magnetism is explained by the main-peak position in the densities of states. The non-linear magnetic couplings and the local environment effects on the local moments are the origin of the itinerant-electron spin glass. Discussions are also given of the magnetism of TM-metalloid amorphous alloys and early TM-TM amorphous alloys. In the former, the hybridization between the metalloid p and TM d orbitals determines their simple magnetism, while in the latter the atomic-size effects play an important role in the concentrated region. The degree of structural and configurational disorder is emphasized as a key factor controlling magnetism in various amorphous alloys.