Atomic-scale structure and electronic property of the La ₂FeCrO₆/SrTiO₃ interface

Combining transmission electron microscopy with first-principles calculations, we investigate atomic-scale structure of a La ₂FeCrO₆/SrTiO₃ interface and related it to its electronic properties at the atomic scale with special focus on the strain effect. We find that the La₂FeCrO₆ film shows a clean and direct contact to the substrate and that an epitaxial, coherent and atomically sharp interface is formed between La₂FeCrO₆ and SrTiO ₃. By estimating the adhesion energies for 21 possible candidate interface geometries, we determine the most stable interface structure theoretically, in consistence with the experimental data. The strain is found to play an insignificant role in affecting interfacial atomic structures, yet impose a substantial electronic impact. The strain induces interfacial electronic states and is responsible for the covalent nature of the interfacial bonding. Moreover, the valence states of Fe and Cr are identified to be +3, and a ferrimagnetic coupling is revealed between Fe and Cr.