Magnetic properties of the ordered and disordered double perovskite Sr2Fe1+xMo1−xO6 (−1 ≤ x ≤ 1/3)

We have studied the effect of cationic disorder on the spin polarization of the double perovskite system Sr 2 Fe 1+ x Mo 1− x O 6 with −1 ≤ x ≤ 1/3. The composition x = 0 corresponds to the well-known double-perovskite Sr 2 FeMoO 6 , 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 .