Room-temperature ferromagnetic properties of. Fe-doped TiO2-δ thin films

Variations of magnetic and electronic properties of reduced anatase and rutile titanium-dioxide (TiO2-delta) thin films through Fe doping have been investigated. For a limited range of Fe content, both anatase and rutile TiO2-delta:Fe films are found to exhibit ferromagnetism at room temperature, as probed by vibrating-sample magnetometry and conversion-electron Mossbauer spectroscopy (CEMS). For the same amount of Fe doping, the anatase sample exhibits a higher magnetic moment than the rutile one. CEMS measurements indicate that Fe3+ ions substituting at octahedral Ti4+ sites contribute to the room-temperature ferromagnetism. Hall-effect measurements show that some of the anatase TiO2-delta:Fe films exhibit a p-type character, but the observed ferromagnetism turns out to be independent of the hole concentration. The observed ferromagnetism in the TiO2-delta:Fe films can be explained in terms of a direct ferromagnetic coupling between two neighboring Fe3+ ions via an electron trapped in a nearby oxygen vacancy.