Antiferromagnetic metal phases in double perovskites having microscopic phase segregation due to strong antisite defect concentration

Recently an antiferromagnetic metal phase has been proposed in double perovskites materials like Sr 2 FeMoO 6 (SFMO), when electron doped. This material has been found to change from half-metallic ferromagnet to a novel antiferromagnetic metal (AFM) upon La-overdoping. The original proposition of such an AFM phase was made for ordered samples, but the experimental realization of La-overdoped SFMO has been found to contain a substantial fraction of antisite defects. A microscopic chemical phase segregation into alternate Fe and Mo rich regions was observed. In this paper we propose a possible scenario in which an antiferromagnetic metal phase can still be stabilized even in presence of such strong antisite defect concentration and phase segregation, by a novel kinetic energy-driven mechanism. Our results thus provide a plausible explanation to the experimental observations in the La-overdoped regime. Antisite regions can thus give rise to antiferromagnetic metallic phases, although the metal is low-dimensional. Copyright EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg 2015