First principles study on magnetic properties of Zn vacancies in ZnO doped with single chalcogen X (X = S, Se, and Te)

First-principles density functional calculations were performed for magnetic properties of wurtzite $ZnO(1-x)Xx$ (X = S, Se, and Te) alloys in the presence of Zn cation vacancies and a low concentration of group-VI dopants in the framework of the local spin density approximation (LSDA) and the LSDA+U method. The positions of the Zn-$3d$ states are misplaced in the LSDA approach and these positions are approximately corrected in the LSDA+U method. We demonstrate that the magnetic state of $ZnO(1-x)Xx$ with a native point defect is mainly localized at the Zn cation vacancy. The substitution of oxygen atoms around the vacancy by chalcogens X does not destroy the local spin triplet state (⁠$ST=1$⁠) at the zinc vacancy but diminishes its stability. The X impurities prefer to be close to the Zn vacancy in the apex position and the destabilization of the magnetic state increases in the series from X = S to X = Te. In order to explain the calculated magnetic properties a group theory analysis has been exploited.