A study was made of vacancy-induced ferromagnetism in the bulk, and at the (10•0) surface, of wurtzite ZnO using density functional theory calculations. It was found that surface vacancies were energetically favoured over bulk vacancies and that the ferromagnetism was induced by Zn vacancies but not by O vacancies. Moreover, local magnetic moments induced at O atoms adjacent to the Zn vacancy were calculated to be larger on the surface than in bulk. These findings indicated that Zn vacancies at surfaces were responsible for the experimentally observed room-temperature ferromagnetism in undoped ZnO thin films and nanoparticles.

Ferromagnetism Induced by Vacancies in Bulk and the (1010) Surfaces of ZnO: Density Functional Theory Calculations. K.Chae, Y.C.Chung, H.Kim: Japanese Journal of Applied Physics, 2011, 50, 01BE05