Effect of oxygen defects on ferromagnetism of Mn doped ZnO

Mn doped ZnO nano-particles were synthesized by a solution route and annealed in N₂, O₂, and Ar, respectively. X-ray diffraction and X-ray photoelectron spectroscopy measurements show that the samples possess typical wurtzite structure and have no other impurity phases. Magnetization loops for ZnO samples were measured and clearly show typical ferromagnetic saturation behavior. With the combination of defect analysis based on photoluminescence spectroscopy and first-principle calculations of the possible magnetic defect centers in Mn doped ZnO, the effect of defects on the nature and origin of ferromagnetism was investigated. The results suggest oxygen vacancies, especially singly ionized oxygen vacancies, play a crucial role in mediating ferromagnetism in the Mn doped ZnO system.