It was found that the strong hybridization between V 3d and O 2p was responsible for the ferromagnetic coupling in this V-doped ZnO system. The presence of VZn increase the covalency between V 3d states and O 2p states and reduce the magnetic moment of V ions. In contrast, the presence of VO broadens the occupied V 3d majority spin states and increases the atomic populations of V 3d orbital. The impurity states of O vacancy and V ions in ZnO have strong interaction and the doped electrons produced by VO were mainly concentrated on the V 3d states, which enhance ferromagnetic interactions in the (V, VO) co-doped ZnO.

Effect of Intrinsic Vacancies on the Ferromagnetism of V-Doped ZnO Based on First-Principles Calculation. W.Yu, H.Liu, L.Zhang, H.Gao, G.Fu: Physica Status Solidi B, 2010, 247[9], 2185–9