Mechanism of room temperature ferromagnetism in ZnO doped with Al

ZnO recently receives extensive interest owing to its potential applications in the dilute magnetic semiconductor. In this work, Al was deposited onto the surface of ZnO film followed by high vacuum annealing. The film showed the room temperature ferromagnetism (RTF). The saturation magnetization (M_s) highly depends on both the thickness of the Al top layer and the thickness of the ZnO film. The RTF disappeared when the film was further annealed in air atmosphere. The detailed structure characterizations (x-ray diffraction and x-ray photoelectron spectroscopy) revealed that the RTF was associated with a charge transfer between Al and Zn.