Antisite domains in double perovskite ferromagnets: Impact on magnetotransport and half-metallicity

Abstract

Several double perovskite materials of the form A2BB′O6 exhibit high ferromagnetic Tc, and significant low-field magnetoresistance. They are also a candidate source of spin-polarized electrons. The potential usefulness of these materials is, however, frustrated by mislocation of the B and B′ ions, which do not organise themselves in the ideal alternating structure. The result is a strong dependence of physical properties on preparative conditions, reducing the magnetization and destroying the half-metallicity. We provide the first results on the impact of spatially correlated antisite disorder, as observed experimentally, on the ferromagnetic double perovskites. The antisite domains suppress magnetism and half-metallicity, as already known from studies of uncorrelated disorder, but lead to a dramatic enhancement of the low-field magnetoresistance.