Effect of Ar Post-irradiations on Magnetic Properties of Cu-Implanted ZnO Single Crystals

Ar+ post-irradiation effects on magnetic behavior of Cu+-implanted ZnO single crystals were studied. It was found that Cu+-implanted and Ar+-irradiated samples, even the primary sample, showed a magnetic moment (MM), but the saturation magnetization (MS) of Ar+ post-irradiated on Cu+ as-implanted one drastically decreased. Based on the first-principle method, it was drawn to the incomplete filling electronic configuration of the substituted Cu ion whose 3d orbital hybridized with O-2p contributing to the magnetism. The MM induced by the substituted Cu+ ion was much less than that induced by the substituted Cu2+ and Cu3+ ion, so the ratio of Cu2+,3+/Cu+ decreased after Ar+ post-irradiation, leading to the decrease of MS. The excessive concentration of O vacancy induced by post-irradiation also weakened the MM by their compensating electrons, and decreased the effective magnetic exchange coupling interaction. Cu-related clusters dissolution was also a critical reason for the reduction of MS.