We have studied the effect of cationic disorder on the spin polarization of the double perovskite system Sr2Fe1+xMo1−xO6 with −1 ≤ x≤ 1/3. The composition x = corresponds to the well-known double-perovskite Sr2FeMoO6, which is expected to have complete spin polarization, however all samples present some degree of Fe/Mo disorder which reduces the tunneling magnetoresistance in granular samples. We consider an electronic model within the renormalized perturbation expansion Green’s functions, consisting in a correlated electron picture with localized Fe-ions and itinerant electrons interacting with the local spins via a double-exchange type mechanism. Our results show the influence of disorder on the density of states and the ground-state properties, particularly on the spin polarization over the whole range of x.
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