Atomic-scale evolution of modulated phases at theferroelectric–antiferroelectric morphotropic phaseboundary controlled by flexoelectric interaction

摘要

Physical and structural origins of morphotropic phase boundaries (mPBs) in ferroics remainelusive despite decades of study. The leading competing theories employ either low-symmetrybridging phases or adaptive phases with nanoscale textures to describe different subsets of themacroscopic data, while the decisive atomic-scale information has so far been missing. Herewe report direct atomically resolved mapping of polarization and structure order parameterfields in a sm-doped BiFeo3system and their evolution as the system approaches a mPB. Wefurther show that both the experimental phase diagram and the observed phase evolution canbe explained by taking into account the flexoelectric interaction, which renders the effectivedomain wall energy negative, thus stabilizing modulated phases in the vicinity of the mPB.our study highlights the importance of local order-parameter mapping at the atomic scale andestablishes a hitherto unobserved physical origin of spatially modulated phases existing in thevicinity of the mPB.