Room-temperature ferromagnetism induced by Cu vacancies in Cux(Cu2O)1-x granular films

Cu-x(Cu2O)(1-x) (0.09 6 <= x <= 1.00) granular films with thickness about 280 nm have been fabricated by direct current reactive magnetron sputtering. The atomic ratio x can be controlled by the oxygen flow rate during Cu-x(Cu2O)(1-x) deposition. Room- temperature ferromagnetism ( FM) is found in all of the samples. The saturated magnetization increases at first and then decreases with the decrease of x. The photoluminescence spectra show that the magnetization is closely correlated with the Cu vacancies in the Cu-x(Cu2O)(1-x) granular films. Fundamentally, the FM could be understood by the Stoner model based on the charge transfer mechanism. These results may provide solid evidence and physical insights on the origin of FM in the Cu2O-based oxides diluted magnetic semiconductors, especially for systems without intentional magnetic atom doping.