Ga-TiO2 films were deposited by pulsed laser deposition. It was found that the as-deposited films exhibited a room-temperature ferromagnetism that depended upon the doping concentration and oxygen partial pressure during the deposition processing. Analysis indicated that the ferromagnetism was not associated with the impurities, but with Ti vacancies, a finding that was verified by positron annihilation spectroscopy. In addition, the possible origins of the ferromagnetism appearing in TiO2 doped with other elements that possessed various valence states, such as Na, Mg, Sn, Ta and W, were considered.

Vacancy-Induced Room-Temperature Ferromagnetism in Ga–TiO2. Bao, N.N., Yi, J.B., Fan, H.M., Qin, X.B., Zhang, P., Wang, B.Y., Ding, J., Li, S.: Scripta Materialia, 2012, 66[10], 821-4