Ferromagnetic properties, electronic structures, and formation energies of Zn vacancy monodoping and (Zn vacancy, Li) codoped ZnO by first principles study

Using the first-principles method based on the density functional theory, we investigated the ferromagnetic properties, electronic structures, and formation energies of Zn vacancy monodoping and (Zn vacancy, Li) codoped ZnO. The results indicate that both cases prefer the ferromagnetic ground state. It was found that the Zn vacancy defect brings a spin polarized state in the nearest neighbor oxygen atoms, and the magnetic moments mainly come from the O atoms surrounding the defect centers, which are different from the conventional diluted magnetic semiconductor. In addition, we found that the spin polarized oxygen atoms have a metallic feature in both spin states and the ferromagnetic exchange interaction among oxygen atoms is mediated by Zn 3d state. Furthermore, it was observed that the replacement of one Zn atom in the system of Zn15O16 by one Li atom can generate holes and reduce the formation energy of Zn vacancy, and then stabilizes the zinc vacancy-including system, resulting in a larger magnetic moment.