Effect of oxygen partial pressure on the ferromagnetism of Cr-doped TiO2 films

Polycrystalline Cr-doped TiO2 films were fabricated by co-sputtering Cr and TiO2 targets in a pure Ar and O-2 mixture with various oxygen partial pressures. Ferromagnetism is observed in all samples and the Curie temperatures are well above 390 K. The saturation magnetization of films shows strong dependence on the oxygen growth pressure while keeping a constant Cr concentration. The ferromagnetism is enhanced in the films deposited at lower oxygen pressures which are thus oxygen deficient, indicating an important role of oxygen vacancies in the ferromagnetic origin of Cr-doped TiO2.