Ferromagnetism induced by Zn vacancy defect and lattice distortion in ZnO

Through the full potential linearized augmented plane wave method, we have explored the vacancy defect induced magnetism in wurtize ZnO. It has been found that the Zn vacancy defect brings a spin polarized state in the nearest neighbor oxygen atoms, whereas the oxygen vacancy defect has no influence on the magnetism. However, it is found that the lattice distortion is a crucial factor for the Zn vacancy induced ferromagnetism because the ferromagnetic ground state cannot be achieved if there is no lattice distortion due to Zn vacancy defect. The magnetic moment of oxygen atom in the nearest neighbor from the Zn vacancy site is ranged from 0.10 to 0.19 μ B and the spin polarized oxygen atoms have metallic feature in both spin states. These results are quite different from those found in other calculation [ Q. Wang , Phys. Rev. B 77 , 205411 ( 2008 ) ]. In addition, we have found that the ferromagnetic exchange interaction among oxygen atoms is mediated by Zn 3 d state. Along with these, the theoretically calculated x-ray absorption spectroscopy and x-ray magnetic circular dichroism are presented.