Electronic structure, optical and ferromagnetic properties of ZnO co-doped with Ag and Co according to first-principles calculations

First-principle calculations were performed to investigate the electronic structure, optical, and ferromagnetic properties of Ag/Co single- and co-doped ZnO. We found that both ZnO single-doped Ag and co-doped Ag/Co exhibit room-temperature ferromagnetism, whereas ZnO single-doped Co shows anti-ferromagnetism. Strongly enhanced room temperature ferromagnetism with saturate magnetization of 10.45 mu(B) has been obtained in ZnO co-doped with Ag/Co, making it a promising room temperature ferromagnetic material. The magnetic moments of Ag/Co co-doped ZnO are mainly derived from the double-exchange effect between Co-3d state and O-2p state, which is consistent with Ruderman-Kittel-Kasuya-Yosida double exchange mechanism theory. In addition, Ag-doped ZnO undergoes a transition from magnetic to non-magnetic with the Ag doping concentration increasing from 2.77 mol% to 5.55 mol%. Ag/Co single- and co-doping can remarkly enhance absorption in the visible range. However, Ag single-doped ZnO has a long carrier lifetime and is conducive to the experimental design and preparation of new photocatalysts. Further research found that the interstitial hydrogen can induce the generation of magnetic order, reduce the magnetic moments and enhance the photocatalytic ability.