Ab initio investigation of the electronic structure of Sr2FeMoO6 double perovskites presenting imperfections

We present ab initio calculations of the electronic structure of Sr2FeMoO6 double perovskites. By considering Fe and Mo antisite defects and oxygen vacancies in various supercells, we investigate their half-metallic character, their magnetic ordering and the hyperfine fields on the Fe and Mo sites. The calculations show that the half-metallic character is lost for all considered antisite defects whereas an oxygen vacancy preserves this character. We exhibit the nearly linear relation between the number of X-O-Y bonds (X, Y = Fe, Mo) and the values of the local magnetic moment and of the hyperfine field on a given atom. The results also suggest that oxygen vacancies can be at the origin of a significant magnetization reduction. (c) 2004 Elsevier B.V. All rights reserved.