Room-temperature ferromagnetism in un-doped ZrO2 thin films

Room-temperature ferromagnetism was observed in un-doped ZrO2 thin films prepared by pulsed electron beam deposition on silicon substrates. In the obtained films, monoclinic and tetragonal phases were both stabilized, with a ratio depending on the oxygen partial pressure during deposition. The ferromagnetism was positively related to the tetragonal phase content, and had a positive linear relationship with the photoluminescence (PL) intensity of emission centred at similar to 420 nm related to the singly ionized oxygen vacancies, as revealed further by the PL analysis. This study suggested that the oxygen vacancies, which stabilized the tetragonal phase at room-temperature, should be the origin of ferromagnetism in un-doped ZrO2 films.