A new class of magnetic materials: Sr2FeMoO6 and related compounds

Ordered double perovskite oxides of the general formula A(2)BB'O-6 have bee n known for several decades to have interesting electronic and magnetic pro perties. However, a recent report of a spectacular negative magnetoresistan ce effect in a specific member of this family, namely Sr2FeMoO6, has brough t this class of compounds under intense scrutiny. It is now believed that t he origin of the magnetism in this class of compounds is based on a novel k inetically-driven mechanism. This new mechanism is also likely to be respon sible for the unusually high temperature ferromagnetism in several other sy stems, such as dilute magnetic semiconductors, as well as in various half-m etallic ferromagnetic systems, such as Heussler alloys. (C) 2001 Elsevier S cience Ltd. All rights reserved.