Ferromagnetism Induced by Vacancies in Bulk and the (1010) Surfaces of ZnO: Density Functional Theory Calculations

Abstract

We studied the vacancy-induced ferromagnetism in bulk and at the (1010) surface of wurtzite ZnO using density functional theory calculations. It is found out that surface vacancies are energetically favored to bulk vacancies and that the ferromagnetism is induced by Zn vacancies but not by O vacancies. Moreover, local magnetic moments induced at O atoms adjacent to the Zn vacancy are calculated to be larger on the surface than in bulk. These findings indicate that Zn vacancies at surfaces are responsible for the experimentally observed room-temperature ferromagnetism in undoped ZnO thin films and nanoparticles.