Effect of the transition metal ratio on bulk and thin slab double perovskite Sr₂FeMoO₆

Double perovskites are promising materials for multiple applications on microelectronics, specially on magnetic devices development. Perhaps the most interesting one is the double perovskite Sr₂FeMoO₆ since its magnetic properties differ from that of other related simple perovskites: SrFeO₃ and SrMoO₃. In this work the evolution of the electronic properties and the magnetic moment distribution as a function of the Fe/Mo ratio in bulk and a thin slab of Sr₂FeMoO₆ was studied. The thin slab was constructed keeping free surfaces parallel to the (001) crystalline planes with different thickness and compositions. All calculations were made in the Density Functional Theory scheme in the Generalized Gradient Approximation, using the Perdew-Burke-Ernzerhof functional, as implemented in the DMol³ code. After being geometry optimized, the electronic Density of States and band structure were calculated, as well as the magnetic moment distribution, for each modeled system. Essential results are as follows: for the bulk cases it was found that half-metallic behavior which characterizes the stoichiometric double perovskite changes if the compound becomes molybdenum or iron rich; for the slab is remarkable the induction of magnetic moments, owed to the corresponding to iron atoms, over their neighbor atoms.