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

The spin-polarized first-principles calculation is performed to investigate the structural, electronic, magnetic and optical properties of the Zn 1 - x Ni x O systems with x=0.00, 0.25, 0.50, 0.75, 1.00. Except for Zn 0.5 Ni 0.5 O with a tetragonal structure, the other Zn 1 - x Ni x O systems are cubic structure. Although pure ZnO is a nonmagnetic semiconductor with a band gap of 1.43 eV, the Zn 0.75 Ni 0.25 O , Zn 0.5 Ni 0.5 O , Zn 0.25 Ni 0.75 O 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 t 2g ( d xy , d yz , d zx ) states with higher energy and doubly degenerate e g ( d z 2 , d x 2 - y 2 ) states with lower energy. The magnetic moments of the Zn 1 - x Ni x O 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 μ tot , conduction band (CB) and valence band (VB) edge spin splittings Δ E C and Δ E V , spin polarized crystal field splittings Δ E ↑ and Δ E ↓ , spin exchange splitting Δ x ( d ) , static dielectric constant ε 1 ( 0 ) and refractive index n ( 0 ) , new appeared small absorption peak at 0–4 eV increase, while the exchange constants N 0 α and N 0 β , original huge narrow absorption peak around 45 eV decrease. [ABSTRACT FROM AUTHOR]