Chemical trends of cation-vacancy-induced d0 ferromagnetism in dilute zinc chalcogenides

The realization of ferromagnetism in d0 semiconductors is important for its applications in spintronics and instructive to the understanding of the magnetic behavior in dilute magnetic semiconductors (DMSs), but its origin is still not fully uncovered, due to the limitation of the density functional used in previous studies. Here, using more sophisticated hybrid functional (HSE06), we reexamine the cation-vacancy induced ferromagnetism in a series of Zn chalcogenides, ZnX (X = O, S, Se, Te), and compare it with previous theoretical studies. The HSE06 calculations show that the spontaneous magnetization of Zn vacancy (VZn) in ZnX is possible, except for ZnTe, due to the more delocalized nature of Te 5p orbitals than O 2p, S 3p and Se 4p orbitals. The ferromagnetic (FM) ground states can then be realized in these systems because the FM coupling between individual VZn could lower energy based on the band-coupling model. Moreover, the HSE06 calculations indicate that the FM coupling gradually increases from ZnO to ZnS and to ZnSe because of the enhanced coupling between the more and more extended defect wavefunctions. The result suggests that it may be more likely to achieve the room-temperature ferromagnetism in ZnS and ZnSe than ZnO, pointing out an alternative way to develop d0 DMSs. Experimental test of the theoretical predictions is called for.