Ferroelectric polarization at grain boundaries and domain walls in multiferroic ε-Fe2O3 films

Abstract

ε-Fe₂O₃ is an attractive magnetoelectric multiferroic material that exhibits ferrimagnetism and ferroelectricity at room temperature and may find applications in next-generation information storage devices. Due to lack of suitable substrates, all the ε-Fe₂O₃ films reported so far are polycrystalline and possess high-density grain boundaries (GBs) and domain walls (DWs). In this study, the atomic structures and ferroelectric polarization of GBs and DWs have been systematically investigated by aberration-corrected transmission electron microscopy. It is found that the polarization directions can be parallel or antiparallel across the GBs and the polarization strength can be enhanced or decreased across the GBs and DWs, which depend closely on the displacement vector and the terminating atomic plane of boundaries. These findings suggest that GBs and DWs play important roles in regulating the ferroelectric properties of ε-Fe₂O₃, thereby introducing fresh perspectives to tailor the ferroelectric properties by grain boundary engineering in magnetoelectric multiferroic materials.