Room-temperature ferromagnetism observed in undoped semiconducting and insulating oxide thin films

Remarkable room-temperature ferromagnetism was observed in undoped TiO2, HfO2, and In2O3 thin films. The magnetic moment is rather modest in the case of In2O3 films on MgO substrates (while on Al2O3 substrates, it is negative showing diamagnetism) when the magnetic field was applied parallel to the film plane. In contrast, it is very large in the other two cases (about 20 and 30 emu/cm(3) for 200-nm-thick TiO2 and HfO2 films, respectively). Since bulk TiO2, HfO2, and In2O3 are clearly diamagnetic, and moreover, there are no contaminations in any substrate, we must assume that the thin film form, which might create necessary defects or oxygen vacancies, would be the reason for undoped semiconducting or insulating oxides to become ferromagnetic at room temperature.