Disorder effects in half-metallic Sr2FeMoO6 single crystals

Abstract

Double perovskites such as Sr2FeMoO6 (SFMO) have been predicted to be half-metallic (100% spin polarized). However, this conclusion is reached under the assumption that SFMO has a perfect crystalline structure. We measure the values of spin polarization P for SFMO single crystals with 11%, 15%, and 16% of B-site disorder using the point contact Andreev reflection technique. The highest spin polarization of P≈70% was determined. Using local spin density approximation, we compute P≈53% for the degree of B-site disorder of 12.5% in good agreement with the experimental results. While our results show that imperfect SFMO is not a half-metal, the observed correlation between the degree of antisite disorder, the magnetic properties, and the values of spin polarization implies that a perfectly ordered SFMO crystal might be half-metallic.