We have investigated the electronic structure of ordered and disordered ${\mathrm{Sr}}_2{\mathrm{FeMoO}}_6$ using ab initio band-structure methods. The effect of disorder was simulated within supercell calculations to realize several configurations with mis-site disorders. It is found that such disorder effects destroy the half-metallic ferromagnetic state of the ordered compound. It also leads to a substantial reduction of the magnetic moments at the Fe sites in the disordered configurations. Most interestingly, it is found for the disordered configurations that the magnetic coupling within the Fe sublattice as well as that within the Mo sublattice always remain ferromagnetic, while the two sublattices couple antiferromagnetically, in close analogy to the magnetic structure of the ordered compound, but in contrast to recent suggestions.

• Received 31 January 2001

DOI:https://doi.org/10.1103/PhysRevB.64.064408