Role of intrinsic defects in ferromagnetism of SnO 2 : First‐principles calculations

The effects of tin interstitial (Sn i ), oxygen vacancy (V O ), and Sn i  + V O defect pair on the electronic structure and magnetic properties of undoped SnO 2 are investigated by means of density functional calculations. Only single positively charged O vacancies V   O 1+can induce local magnetic moments in bulk SnO 2 . The magnetic coupling between two V   O 1+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 V   O 1+ . Consequently, the magnetic coupling calculated by GGA +  U S becomes antiferromagnetic, which shows that a self‐consistent bandgap correction is essential for the correct description of the magnetism in widegap SnO 2 . The results indicate that O vacancy in bulk SnO 2 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 SnO 2 .