Abstract
The electronic structures and magnetic properties of double perovskites Sr 2 FeMoO 6 , Sr 2 FeReO 6 , and Sr 2 CrWO 6 have been studied by using the full-potential linear muffin-tin orbital method within the local-spindensity approximation (LSDA) and the generalized gradient approximation (GGA). The on-site Coulomb energy U has also been taken into account in both schemes (LSDA+U and GGA+U). The results predict a half-metallic ferrimagnetic band structure with total spin magnetic moment of 4μ B , 3μ B , and 2μ B per formula unit for Sr 2 FeMoO 6 , Sr 2 FeReO 6 , and Sr 2 CrWO 6 , respectively. By including the spin-orbit coupling in the self-consistent calculations, we find that the 5d transition-metal atoms W and Re exhibit large unquenched orbital magnetic moments because of significant spin-orbit interaction in 5d orbitals. On the other hand, in Fe and Cr 3d and Mo 4d orbitals, the orbital moments are all quenched even though the on-site Coulomb energy U is taken into account. This is in strong contrast to the enhanced large 3d orbital moments in CoO and NiO but similar to the quenched orbital moment in CrO 2 .