Structural, electronic, magnetic and optical properties of Zn1-xNixO from first-principles

Abstract

The spin-polarized first-principles calculation is performed to investigate the structural, electronic, magnetic and optical properties of the Zn1-xNixO systems with x=0.00, 0.25, 0.50, 0.75, 1.00. Except for Zn0.5Ni0.5O with a tetragonal structure, the other Zn1-xNixO systems are cubic structure. Although pure ZnO is a nonmagnetic semiconductor with a band gap of 1.43eV, the Zn0.75Ni0.25O, Zn0.5Ni0.5O, Zn0.25Ni0.75O and NiO systems are completely half metal and thus usable in spintronic devices. The tetrahedral crystal field of the surrounding four O anions splits Ni-3d states into triply degenerate t2g(dxy,dyz,dzx) states with higher energy and doubly degenerate eg(dz2,dx2-y2) states with lower energy. The magnetic moments of the Zn1-xNixO systems are mainly contributed by Ni atom with the small parallel contributions of O and Zn atoms. With increasing Ni concentration, the atomic magnetic moments μ¯Ni, μ¯O, and μ¯Zn, total magnetic moment μtot, conduction band (CB) and valence band (VB) edge spin splittings ΔEC and ΔEV, spin polarized crystal field splittings ΔE↑ and ΔE↓, spin exchange splitting Δx(d), static dielectric constant ε1(0) and refractive index n(0), new appeared small absorption peak at 0–4eV increase, while the exchange constants N0α and N0β, original huge narrow absorption peak around 45eV decrease.