Emergent Antipolar Phase in BiFeO<sub>3</sub>–La<sub>0.7</sub>Sr<sub>0.3</sub>MnO<sub>3</sub> Superlattice
Wen Dong, Jonathan J. P. Peters, Dorin Rusu, Michael Staniforth, Alan E. Brunier, James Lloyd‐Hughes, Ana M. Sánchez, Marin Alexe
Abstract
Ferroelectric–paraelectric superlattices show emerging new states, such as polar vortices, through the interplay and different energy scales of various thermodynamic constraints. By introducing magnetic coupling at BiFeO3–La0.7Sr0.3MnO3 interfaces epitaxially grown on SrTiO3 substrate, we find, for the first time in thin films, a sub-nanometer thick lamella-like BiFeO3. The emergent phase is characterized by an arrangement of a two unit cell thick lamella-like structure featuring antiparallel polarization, resulting an antiferroelectric-like structure typically associated with a morphotropic phase transition. The antipolar phase is embedded within a nominal R3c structure and is independent of the BiFeO3 thickness (4–30 unit cells). Moreover, the superlattice structure with the morphotropic phase demonstrates azimuth-independent second harmonic generation responses, indicating a change of overall symmetry mediated by a delicate spatial distribution of the emergent phase. This work enriches the understanding of a metastable state manipulated by thermodynamic constraints by lattice strain and magnetic coupling.