Dominant ferromagnetic coupling over antiferromagnetic in Ni doped ZnO: first-principles calculations

Abstract

The low magnetic moment (MM) in diluted magnetic semiconductors (DMS) at low impurity doping levels has triggered considerable research into condensed magnetic semiconductors (CMS).This work reports an ab-initio investigation of the electronic structures and magnetic properties of ZnO in a zinc-blende (ZB) structure doped with nickel ions. Ni-doped ZnO-based DMS and CMS exhibit a dominance of ferromagnetic coupling over antiferromagnetic. A robust increase in the magnetization has been observed as a function of Ni impurity levels. This material favors short-range magnetic interactions at the ground state, suggesting that the observed ferromagnetism is defined by the double exchange mechanism. The spin-polarized density of states (DOS) of Ni-doped ZnO characterizes it as half-metallic with a considerable energy gap for up-spin components and as metallic for-down spins. Half-metallic Ni:ZnO based magnetic semiconductors with high magnetization are expected to have potential applications in spintronics.