Ferromagnetic properties, electronic structures, and formation energies of Zn vacancy monodoping and (Zn vacancy, Li) codoped ZnO by first principles study

► Zn vacancy monodoping and (Zn vacancy, Li) codoped ZnO prefer the ferromagnetic state. ► The magnetic moments were mainly contributed by the spin polarized O atoms. ► Spin polarized oxygen atoms present a metallic feature in both spin states. ► Ferromagnetic exchange interaction among oxygen atoms is mediated by Zn 3d state. ► The replacement of a Zn in Zn15O16 by one Li results in a larger magnetic moment.