Nitrogen doping-mediated room-temperature ferromagnetism in insulating Co-doped SnO2 films

Co-doped SnO2 films codoped with nitrogen (N) have been prepared by magnetron sputtering to investigate the effect of p-type defects on magnetic properties. The incorporation of N modifies the preferential growth orientation of the films. Multiple characterization techniques reveal that the incorporated Co2+ and N3− ions substitute for Sn4+ and O2− sites in SnO2 lattice, respectively. As N concentration increases, the band gap of the films decreases because of the formation of Sn-N bond. Room-temperature ferromagnetism is observed in (Co, N)-codoped SnO2 films, and the saturated magnetic moment is sensitive to the incorporated N concentration. The variations in the magnetic properties as a function of N concentration are discussed on the basis of bound magnetic polaron model.