First-principles study on the coexistence of different valence states of Zn vacancy, Cu1+/2+ doping, and Hi in ZnO magnetic switch

In this study, we used first principles to investigate the magnetic sources and switches of Zn34Cu1+HiO36(VZn0), Zn34Cu1+HiO36(VZn2−), Zn34Cu2+HiO36(VZn0), and Zn34Cu2+HiO36(VZn2−) systems. On the basis of formation energy, phonon spectrum, and temporal variation of energy, we concluded that the above systems were all in a stable state. The doped system can be magnetized by adjusting the valence state of Zn vacancy, and the Zn34Cu1+HiO36(VZn0) and Zn34Cu2+HiO36(VZn2−) systems demonstrated magnetism. We found that the Zn34Cu1+HiO36(VZn0) system acquired magnetism through (O.↓↑+VZn")x⇔(↑O.+VZn"+↑O.)x⇔(↑O.+VZn"+↓O.)x super- and double-exchange interactions, whereas the magnetism of the Zn34Cu2+HiO36(VZn2−) system originated mainly from the action of the O1−–VZn2−–Cu2+-bound magnetic polaron and double exchange. Our theory provides a new approach for the use of magnetic switches in magnetic semiconductors.