Ab initio study of the anion vacancy on anatase TiO2 (101) surface

In this study, we have studied the electronic structure and magnetic properties of oxygen vacancy on anatase TiO 2 (101) surface using density functional theory (DFT) calculations. The results show that only the vacancy of threefold-coordinated oxygen ( O 3c ) can introduce the magnetism on (101) surface. The spins induced by the O 3c vacancy will form a stable ferromagnetic state, and it can introduce a magnetic moment of 1.05 μ B . Moreover, the magnetic moment mainly results from the d orbitals of three low-charge-state Ti ions adjacent to the O 3c vacancy. The O 3c vacancy on (101) surface can also result in a localized state of spin polarization in the bandgap, which is about 0.22 eV below the Fermi energy. Our findings imply that the oxygen vacancy on the surface may be responsible for the unexpected ferromagnetism in pristine TiO 2 film. The experimentally observed d 0 -ferromagnetism behavior in TiO 2 system is in good agreement with our calculated results.