Effect of non-magnetic impurities on the magnetic states of anatase TiO₂.

The electronic and magnetic properties of TiO₂, TiO₁.₇₅, TiO₁.₇₅N₀.₂₅, and TiO₁.₇₅F₀.₂₅ compounds have been studied by using ab initio electronic structure calculations. TiO₂ is found to evolve from a wide-band-gap semiconductor to a narrow-band-gap semiconductor to a half-metallic state and finally to a metallic state with oxygen vacancy, N-doping and F-doping, respectively. The present work clearly shows the robust magnetic ground state for N-and F-doped TiO₂. The N-doping gives rise to a magnetic moment of ~ 0.4 μ(B) at the N site and ~ 0.1 μ(B) each at two neighboring O sites, whereas F-doping creates a magnetic moment of ~ 0.3 μ(B) at the nearest Ti atom. Here we also discuss the possible cause of the observed magnetic states in terms of the spatial electronic charge distribution of Ti, N, and F atoms responsible for bond formation.