First-principles investigations of orbital magnetic moments and electronic structures of the double perovskites Sr2FeMoO6, Sr2FeReO6, and Sr2CrWO6 -: art. no. 094438

The electronic structures and magnetic properties of double perovskites Sr2FeMoO6, Sr2FeReO6, and Sr2CrWO6 have been studied by using the full-potential linear muffin-tin orbital method within the local-spin-density 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 4mu(B), 3mu(B), and 2mu(B) per formula unit for Sr2FeMoO6, Sr2FeReO6, and Sr2CrWO6, 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 CrO2.