Condensed Matter Seminars

Sr2FeMoO6 is a magnetic metal with an unusually high Curie temperature (~ 420 K) and belongs to the double perovskite family of compounds. It shot in to fame a few years ago due to its remarkable magnetoresistive properties. [1] We discuss the origin of ferromagnetism in this and related compounds based on a mechanism driven by the kinetic energy, [2-4] establishing these as members of a new class of magnetic materials; this mechanism also explains [4,5] the occurrence of ferromagnetism in dilute magnetic semiconductors, such as Mn-doped GaAs and in pyrochlore, Tl2Mn2O7. [6] We also show [7] that the magnetoresistance in Sr2FeMoO6 arises from a magnetically triggered nearly-resonant tunnelling condition in contrast to other mechanisms discussed so far in the context of CMR and GMR materials.