Electronic structure and magnetic properties of the N monodoping and (Li, N)-codoped ZnO

Using first-principles calculations based on density functional theory, we investigated systematically the electronic structures and magnetic properties of N monodoping and (Li, N) codoping in ZnO. The results indicate that monodoping of N in ZnO favors a spin-polarized state with a magnetic moment of 0.95 μB per supercell and the magnetic moment mainly comes from the unpaired 2p2p electrons of N and O atoms. In addition, it was found that monodoping of N in ZnO is a weak ferromagnet and it is the spin-polarized O atoms that mediate the ferromagnetic exchange interaction between the two N atoms. Interestingly, by Li substitutional doping at the cation site (LiZn), the ferromagnetic stability can be increased significantly and the formation energy can be evidently reduced for the defective system. Therefore, we think that the enhancement of ferromagnetic stability should be attributed to the accessorial holes and the lower formation energy induced by LiZn doping.

Research highlights
► N monodoped ZnO favors spin-polarized state with a magnetic moment of 0.95 μB per supercell.
► The magnetic moment mainly comes from the unpaired 2p2p electrons of N and O atoms.
► The monodoping of N in ZnO is a weak ferromagnet.
► Spin-polarized O atoms mediate ferromagnetic exchange interaction between two N atoms.
► Ferromagnetic (FM) stability can be increased by replacing a Zn with a Li (LiZn).
► The enhancement of FM stability should be attributed to the accessorial holes and the lower formation energy induced by LiZn.