Role of intrinsic defects in ferromagnetism of SnO2: First-principles calculations

Abstract

The effects of tin interstitial (Sni), oxygen vacancy (VO), and Sni + VO defect pair on the electronic structure and magnetic properties of undoped SnO2 are investigated by means of density functional calculations. Only single positively charged O vacancies V1+O can induce local magnetic moments in bulk SnO2. The magnetic coupling between two V1+O calculated by generalized gradient approximation (GGA) is ferromagnetic. Self-consistent bandgap correction, which is achieved by adding a Coulomb U on O-2s orbital, results in the full occupation of the spin-up gap state of V1+O. Consequently, the magnetic coupling calculated by GGA + US becomes antiferromagnetic, which shows that a self-consistent bandgap correction is essential for the correct description of the magnetism in widegap SnO2. The results indicate that O vacancy in bulk SnO2 cannot induce ferromagnetism, which suggests that the atoms or defects located at the surface or substrate interface may play a key role in turning the ferromagnetism observed in undoped SnO2. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.