Electronic, magnetic, optical and thermoelectric properties of Ca2Cr1-xNixOsO6 double perovskites

摘要

With the help of density functional theory calculations, we explored the recently synthesized double perovskite material Ca2CrOsO6 and found it to be a ferrimagnetic insulator with a band gap of similar to 0.6 eV. Its effective magnetic moment is found to be similar to 0.23 mu(B) per unit cell. The proposed behavior arises from the cooperative effect of spin-orbit coupling and Coulomb correlation of Cr-3d and Os-5d electrons along with the crystal field. Within the ferrimagnetic configuration, doping with 50% Ni in the Cr-sites resulted in a half-metallic state with a total moment of nearly zero, a characteristic of spintronic materials. Meanwhile, the optical study reveals that both epsilon(xx)(1) and epsilon(zz)(1) decrease first and then increase rapidly with increasing photon energy up to 1.055 eV. We also found optical anisotropy up to similar to 14 eV, where the material becomes almost optically isotropic. This material has a plateau like region in the sigma(xx) and sigma(zz) parts of the optical conductivity due to a strong 3d-5d interband transition between Cr and Os. In addition, we performed thermoelectric calculations whose results predict that the material might not be good as a thermoelectric device due to its small power factor.