Magnetism, magneto-transport and other properties of Fe-Mo based double perovskites

D.D. Sarma

Solid State and Structural Chemistry Unit

Indian Institute of Science

Bangalore 560012

Sr2FeMoO6 is known to be a ferromagnet with a remarkably high Tc (~ 420 K). In fact, the class of double perovskite oxides, that this compound belongs to, is filled with examples of ferromagnets with unusually high Tc and antiferromagnets with very low TN. We provide a microscopic understanding, based on a kinetically-driven mechanism, for the occurrence of such high Tc in some of the members of the series, while some others exhibit a low TN. This new mechanism is also likely to be responsible for ferromagnetism in several other systems, such as dilute magnetic semiconductors, as well as in various other half-metallic ferromagnetic systems, such as Heussler alloys. I shall underline the similarities between the physics of the double perovskites and the dilute magnetic semiconductors with new experimental results as well as theoretical considerations.

It is interesting to note that while Sr2FeMoO6 is ferromagnetic metal, closely related Sr2FeWO6 is an antiferromagnetic insulator. It is possible to synthesise the entire range of solid solution, Sr2FeMoxW1-xO6, between these two end compositions, assuring one of both a metal-insulator and a magnetic transition. If time permits, I shall discuss these transitions in Sr2FeMoxW1-xO6 and present a T-x phase diagram of this solid solution.