Ab initio study of the electronic and magnetic properties of Sr2-xLaxFe1+y/2Mo1-y/2O6 double perovskites

Using the first-principles full potential linearized augmented plane wave method, the electronic structure of Sr2-xLaxFe1+y/2Mo1-y/2O6 (SLFMO) double-perovskite systems is investigated for x = 1/2 and 1 and for y =+ 1 and - 1. Substituting Sr atoms by La atoms allows one to tune the electrons added into the minority spin band and enhances the half-metal feature - according to the rigid band shift model - even if the magnetization decreases with increasing La concentration. By taking into account the chemical disorder on the Fe and Mo sites, resulting from the introduction of La as shown experimentally, it is shown (i) that a supplemental magnetization reduction occurs because the magnetic moment on the Fe antisite is opposite to the one on the Fe regular sites and (ii) that the half-metal feature is preserved in SLFMO for x = 1/2 and 1 contrary to the case for SFMO. Finally, because surface or interface Fe deficiency should have a more limited impact on the spin polarization than for SFMO, SLFMO/SrTiO3 multilayers are investigated in order to confirm this prediction by determining the spin polarization at the interface, which is found to remain high. (paper)