Dislocation-tuned ferroelectricity and ferromagnetism of the BiFeO3/SrRuO3 interface

Misfit dislocations at a heteroepitaxial interface produce huge strain and, thus, have a significant impact on the properties of the interface. Here, we use scanning transmis-sion electron microscopy to demonstrate a quantitative unit-cell-by-unit-cell mapping of the lattice parameters and octahedral rotations around misfit dislocations at the BiFeO3/SrRuO3 interface. We find that huge strain field is achieved near dislocations, i.e., above 5% within the first three unit cells of the core, which is typically larger than that achieved from the regular epitaxy thin-film approach, thus significantly altering the magnitude and direction of the local ferroelectric dipole in BiFeO3 and magnetic moments in SrRuO3 near the interface. The strain field and, thus, the structural dis-tortion can be further tuned by the dislocation type. Our atomic-scale study helps us to understand the effects of dislocations in this ferroelectricity/ferromagnetism heterostructure. Such defect engineering allows us to tune the local ferroelectric and ferromagnetic order parameters and the interface electromagnetic coupling, providing new opportunities to design nanosized electronic and spintronic devices.

Automated summary

We used scanning transmission electron microscopy to quantitatively map the lattice parameters and octahedral rotations around misfit dislocations at the BiFeO3/SrRuO3 interface. We found that a huge strain field is achieved near the dislocations, significantly altering the local ferroelectric dipole and magnetic moments near the interface. The strain field and structural distortion can be further tuned by the dislocation type. Our atomic-scale study helps us understand the effects of dislocations in this ferroelectricity/ferromagnetism heterostructure, providing opportunities for designing nanosized electronic and spintronic devices through defect engineering.