Magnetism in Double Perovskites

Double-perovskite compounds with general formula ABB'O-6, have attracted a lot of attention in recent years due to a variety of properties exhibited by them. In this paper, we will review our recent study on a number of double-perovskite compounds, namely La-doped Sr2FeMoO6, Cr-based family of compounds, Sr2CrXO6 (X = W, Re, Os), characterized with spectacularly high ferromagnetic transition temperatures and the magneto-capacitive compound, La2NiMnO6, We will discuss the signature of hybridization-driven antiferromagnetism in La-doped Sr2FeMoO6, while the parent compound, Sr2FeMoO6, is a half-metallic ferromagnet. The magnetism in the 3d-5d double perovskite Sr2CrXO6 (X = W, Re, Os) is found to be driven by the interplay of the hybridization-driven mechanism and the superexchange, which resulted into progressive increase of T-c as one moves from W to Re to Os at the B' site. Our work, in the context of La2NiMnO6, identifies its superexchange-driven microscopic origin being responsible for the near room-temperature insulating ferromagnetic behavior.