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 similar to 0.4 mu(B) at the N site and similar to 0.1 mu(B) each at two neighboring O sites, whereas F-doping creates a magnetic moment of similar to 0.3 mu(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.