An interesting magnetoresistive system:$Sr_2FeMoO_6$

Ordered double perovskite oxides of the general formula, $A_2BB'O_6,$ have been known for several decades to have interesting electronic and magnetic properties. However, a recent report of a spectacular negative magnetoresistance effect in a specific member of this family, namely $Sr_2FeMoO_6,$ has brought this class of compounds under intense scrutiny. In this small review, we present few theoretical and experimental results, describing mainly the effects of Fe/Mo antisite defects on the properties of this compound and also briefly discuss few other puzzling facts about this fascinating compound