First-principles study of electron doping and disorder effects on electronic and magnetic properties in Sr_(2-x)Nd_xFeMoO_6 double perovskites

摘要

We have investigated the electronic and magnetic properties of electron-doped Sr_(2-x)Nd_xFeMoO_6 (x = 0.0, 0.25, 0.5) using first-principles density functional theory within the generalized gradient approximation (GGA) and GGA+U schemes. Our results'reveal that the structural-phase transition occurs for the composition x = 0.5 and the unit cell volume remains nearly constant from x = 0.0 to x = 0.25. The magnetic moment of the Mo site increases distinctly on electron doping and the doped electrons are considered to occupy mainly the down-spin Mo 4d band from the band calculation. We also have performed the electronic structure calculations for pure and doped Sr_2FeMoO_6 with positional disorder at the Fe/Mo sites. Disordering is found to destroy the half-metallic nature of the ordered compound; moreover, disorder leads to a significant reduction in the net magnetic moment. It is found that the rapid reduction in the magnetic moment is mainly caused by the antiferromagnetic interaction between Fe-O-Fe and the electron doping effects.