The dual effects of Al-doping on the ferromagnetism of Zn0.98–yEr0.02AlyO thin films

Zn0.98–yEr0.02AlyO (0 ≤ y ≤ 0.04) thin films have been prepared by inductively coupled plasma enhanced physical vapor deposition method. It is found that Er3+ substitutes Zn2+ in ZnO lattice without forming any magnetic secondary phase. Al-doping has dual effects on the electron transport and magnetic properties of Er-doped ZnO films, wherein AlZn and Ali play different roles. When 0 ≤ y ≤ 0.02, the dominant AlZn increases and induces both carrier concentration and saturation magnetization (Ms) increasing. When 0.02 < y ≤ 0.04, Ali becomes main defect and enhances the probability of electron scattering, thus reduces the Ms.