Role of O defects at the BiMnO3/SrTiO3 interface

Abstract

We use first principles calculations to study ideal and O deficient BiMnO _3 /SrTiO _3 superlattices. The ideal superlattice is characterized by parallel alignment of the Mn and Ti magnetic moments at the n -interface, while an antiparallel alignment has been reported experimentally. O defects at the n -interface are found to favor the MnO _2 and BiO layers over the TiO _2 layer. The band gap of the superlattice is strongly reduced when the MnO _2 layer is O deficient and ${d}_{3{z}^{2}-{r}^{2}}$ states are observed at the Fermi energy when the BiO layer is O deficient. Only in the latter case the Mn and Ti magnetic moments at the n -interface align antiparallel. Therefore, O defects in the BiO layer turn out to be essential for reproducing the experimental interface magnetism and for understanding its mechanism.

Keywords

• interface
• magnetism
• heterostructure