Effects of oxygen vacancy location on the electronic structure and spin density of Co-doped rutile TiO2 dilute magnetic semiconductors

According to density functional theory (DFT) using the plane wave base and pseudo-potential, we investigate the effects of the specific location of oxygen vacancy (VO) in a (Ti,Co)O6 distorted octahedron on the spin density and magnetic properties of Co-doped rutile TiO2 dilute magnetic semiconductors. Our calculations suggest that the VO location has a significant influence on the magnetic moment of individual Co cations. In the case where two Co atoms are separated far away from each other, when the VO is located at the equatorial site of a Co-contained octahedron, the ground state of the two Co cations is d6(t32g ↑,t32g ↓) without any magnetic moment. However, if the VO is located at the apical site, these two Co sites have different ground states and magnetic moments. The spin densities are also observed to be modified by the exchange coupling between the Co cations and the location of VO. Some positive spin polarization is induced around the adjacent O ions. (condensed matter: electronic structure, electrical, magnetic, and optical properties)