Electronic and Magnetic Properties of Ni-Doped Zinc-Blende ZnO: A First-Principles Study

Abstract

The electronic structure, band structure, density of state, and magnetic properties of Ni-doped zinc-blende (ZB) ZnO are studied by using the first-principles method based on the spin-polarized density-functional theory. The calculated results show that Ni atoms can induce a stable ferromagnetic (FM) ground state in Ni-doped ZB ZnO. The magnetic moments mainly originate from the unpaired Ni 3d orbitals, and the O 2p orbitals contribute a little to the magnetic moments. The magnetic moment of a supercell including a single Ni atom is 0.79 μ_B. The electronic structure shows that Ni-doped ZB ZnO is a half-metallic FM material. The strong spin-orbit coupling appears near the Fermi level and shows obvious asymmetry for spin-up and spin-down density of state, which indicates a significant hybrid effects from the Ni 3d and O 2p states. However, the coupling of the anti-ferromagnetic (AFM) state show metallic characteristic, the spin-up and spin-down energy levels pass through the Fermi surface. The magnetic moment of a single Ni atom is 0.74 μ_B. Moreover, the results show that the Ni 3d and O 2p states have a strong p-d hybridization effect near the Fermi level and obtain a high stability. The above theoretical results demonstrate that Ni-doped zinc blende ZnO can be considered as a potential half-metal FM material and dilute magnetic semiconductors.

Keywords: Ni-doped; ZnO; ferromagnetic and anti-ferromagnetic; first-principles.

Figure 1

The crystal model of Ni-doped zinc-blende (ZB) ZnO (the gray and white balls indicate Zn and O atoms, respectively). The positions of Zn substituted by Ni are denoted by 1 and 2–3, (a) 2 × 2 × 2 supercell; (b) 1 × 2 × 2 supercell.

Figure 2

(a) Band structure of pure ZB ZnO; (b) Total DOS of pure ZB ZnO.

Figure 3

Band structures of Ni-doped ZB ZnO. (a) FM; (b) AFM.

Figure 3

Band structures of Ni-doped ZB ZnO. (a) FM; (b) AFM.

Figure 4

Total and partial DOS of Ni-doped ZB ZnO. (a) total DOS of FM; (b) partial DOS of Ni atoms for FM; (c) partial DOS of Ni 3d and O 2p for FM; (d) total DOS of AFM; (e) partial DOS of Ni atoms for AFM; (f) partial DOS of Ni 3d and O 2p for AFM.

Figure 5

Energy graph of 3d transition-metal atoms in a tetrahedral crystal field (T_d).