In-Situ Atomic-Scale Observation of Brownmillerite to Ruddlesden-Popper Phase Transition Tuned by Epitaxial Strain in Cobaltites  

作　　者：林挺 高昂 汤哲歆 林炜光 孙慕华 张庆华 王雪锋 郭尔佳 谷林 Ting Lin;Ang Gao;Zhexin Tang;Weiguang Lin;Muhua Sun;Qinghua Zhang;Xuefeng Wang;Er-jia Guo;Lin Gu(Beijing National Laboratory for Condensed Matter Physics,Institute of Physics,Chinese Academy of Sciences,Beijing 100190,China;School of Physical Sciences,University of Chinese Academy of Science,Beijing 100049,China;Beijing National Center for Electron Microscopy and Laboratory of Advanced Materials,Department of Materials Science and Engineering,Tsinghua University,Beijing 100084,China;Department of Physics&Center of Materials Science and Optoelectronics Engineering,University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]Beijing National Laboratory for Condensed Matter Physics,Institute of Physics,Chinese Academy of Sciences,Beijing 100190,China [2]School of Physical Sciences,University of Chinese Academy of Science,Beijing 100049,China [3]Beijing National Center for Electron Microscopy and Laboratory of Advanced Materials,Department of Materials Science and Engineering,Tsinghua University,Beijing 100084,China [4]Department of Physics&Center of Materials Science and Optoelectronics Engineering,University of Chinese Academy of Sciences,Beijing 100049,China

出　　处：《Chinese Physics Letters》2024年第4期152-158,共7页中国物理快报（英文版）

基　　金：supported by the National Natural Science Foundation of China(Grant Nos.52322212,52072400,52025025,and 52250402)。

摘　　要：Phase transitions involving oxygen ion extraction within the framework of the crystallographic relevance have been widely exploited for sake of superconductivity,ferromagnetism,and ion conductivity in perovskiterelated oxides.However,atomic-scale pathways of phase transitions and ion extraction threshold are inadequately understood.Here we investigate the atomic structure evolution of LaCoO_(3) films upon oxygen extraction and subsequent Co migration,focusing on the key role of epitaxial strain.The brownmillerite to Ruddlesden-Popper phase transitions are discovered to stabilize at distinct crystal orientations in compressive-and tensile-strained cobaltites,which could be attributed to in-plane and out-of-plane Ruddlesden-Popper stacking faults,respectively.A two-stage process from exterior to interior phase transition is evidenced in compressive-strained LaCoO_(2.5),while a single-step nucleation process leaving bottom layer unchanged in tensile-strained situation.Strain analyses reveal that the former process is initiated by an expansion in Co layer at boundary,whereas the latter one is associated with an edge dislocation combined with antiphase boundary.These findings provide a chemomechanical perspective on the structure regulation of perovskite oxides and enrich insights into strain-dependent phase diagram in epitaxial oxides films.

关 键 词：STRAINED Phase OXIDES 

分 类 号：O469[理学—凝聚态物理]