Defect-induced structural and ferromagnetic properties of hydrogenated Mn-doped ZnO film

The influence of hydrogenated annealing temperature on the room temperature ferromagnetism of Mn-doped ZnO films was investigated. The X-ray diffraction and X-ray photoelectron spectra reveal Mn²⁺ ions have been incorporated into wurtzite ZnO lattices. The saturation magnetization increases quickly with the increasing N₂/H₂-annealing temperature (T_an) until the temperature reaches 750 °C, and then the saturation magnetization approaches a constant value. Some foamlike materials appear in the non-continuous films when the T_an is 640 °C or above, and saturation magnetization of these films become stronger than that of the (600–630 °C) annealed films. The results of X-ray photoelectron spectra, SEM images and photoluminescence spectrum suggest that oxygen vacancy concentration of the annealed films increases with increasing T_an, which leads to the ferromagnetism of the Mn-doped ZnO film. These results demonstrate that oxygen vacancies, especially singly ionized oxygen vacancies, play a crucial role in mediating ferromagnetism of the Mn-doped ZnO film.