Perovskite and spinel structures are widely found in ferroelectric and magnetic oxides, respectively, making their combination important for multiferroic composites. In this study, the (111) interface between perovskite-type BiFeO3 and spinel-type NiFe2O4, has been systematically investigated at the atomic scale combining aberration-corrected scanning transmission electron microscopy and first-principles calculations. The atomic terminations at the interface were determined to be the BiO3 layer on the BiFeO3 side and the tetrahedral Fe layer on the NiFe2O4 side. The lattice mismatch between BiFeO3 and NiFe2O4 is primarily accommodated by the first and second BiO3 layers inside BiFeO3, indicating a stand-off of misfit dislocations in BiFeO3. A metallic interface is formed between the two insulating phases, with the BiO3 and tetrahedral Fe layer coupled antiferromagnetically across the interface. The magnetic moment in NiFe2O4 and the ferroelectric polarization in BiFeO3 drop slightly at the interface and return to the bulk values within two atomic layers from the interface.
- TOTAL-ENERGY CALCULATIONS