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 Sr2FeMoO6 (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