It was recalled that room-temperature ferromagnetism with a large magnetic moment was observed in undoped HfO2 films grown onto Y-stabilized zirconia substrates. It was known that neither Hf4+ nor O2- was magnetic. On the other hand, bulk HfO2 was clearly diamagnetic. It was not possible to attribute such a large magnetic moment to impurities. It was deduced that the thin-film form, which could create necessary defects and/or O vacancies, must be the main reason for the undoped insulating oxide becoming ferromagnetic. The filling-up of O vacancies reduced the magnetic moment enormously and, at some critical point, destroyed the ferromagnetic ordering completely. This confirmed the assumption that magnetism in HfO2 thin films originated from defects and/or O vacancies. The defects seem to be located mainly at the interface between the film and the substrate.

Magnetism due to Defects/Oxygen Vacancies in HfO2 Thin Films. N.H.Hong: Physica Status Solidi C, 2007, 4[3], 1270-5