单轴应变锰氧化物外延膜中相分离畴结构的有序化及其成像演化动力学

Strongly correlated perovskite manganites exhibit ubiquitously multiscale phase separation behavior, which is closely related to its physical properties, such as, colossal magnetoresistance, metal-insulator phase transition. Recently, with the progress of new technology to directly characterize the phase separation and to fabricate manganite micro-/nanostructured patterns, the interest in phase separation moves to reveal the origin of phase separation mechanism and domain evolution. On the one hand, the formation and orientation of domain configuration can be guided by anisotropic strain states, giving rise to anisotropic percolating channels and anisotropic magnetoresistance. On the other hand, low-dimensional manganite nanostructures, especially when the width of micro-/nanostructures is comparable to the length scale of phase separation, dispaly several fasinating phenomena, including giant discrete steps in metal-insulator transition and intrinsic tunneling, implying that the low-dimensional micro-/nanostructures of manganites contains essential dynamics of domain evolution in phase separation. Much efforts have been done to explore mesoscopic texture of phase competition and coexsitence, and the phase-separated domain configurations are subjected to anisotropic strain, chemical ordering, spatial confinement etc. However, it still remains elusive. Manganite films are a protypical system to exhibit phase separation behavior. Combined with its corresponding microscale samples using focused ion beam milling, the further understaning of phase-separated dynamics will provide a prerequsite ingredient for future application of functional devices based on manganites. In this project, we focus on the domain dynamics of uniaxially strained manganite films and its spatially confined microscale structures, and explore how to control the ordering of domain configurations, in which the volume fraction of antiferromagnetic phase can be tuned by multiple parameters. The demonstration of the evolution, dynamics and control of domain configuration will be significant for the development of oxide electronics.

强关联钙钛矿锰氧化物展示多尺度多相共存相分离行为，与其庞磁阻、金属绝缘转变等物理性能密切相关。近期研究表明各向异性应变、化学掺杂、空间约束等因素影响相分离结构，一方面各向异性应变诱导优先取向的畴结构图案，形成各向异性导电逾渗通道；另一方面空间约束低维结构展示有趣的内禀遂穿磁阻等输运行为，预示着微纳尺度的锰氧化物低维结构蕴含着本征的相分离畴演化动力学。因此，选取单轴应变调控的锰氧化物外延膜，多参量调控其反铁磁相体积分数；开展外延薄膜及其离子束蚀刻的微纳加工样品的相分离畴结构表征、畴结构有序化调控、及其演化动力学研究；是构筑锰氧化物微纳尺度功能器件的必要前提。本项目以单轴应变锰氧化物外延薄膜及其空间约束的低维结构为主干，重点研究不同反铁磁相体积分数外延膜的反铁磁相动力学、空间约束对于畴结构演化的影响规律及畴结构有序化调控，为氧化物自旋电子学的发展提供实验基础。

本项目以单轴应变锰氧化物外延薄膜及其空间约束的低维结构为主干，重点研究不同反铁磁相体积分数外延膜的反铁磁相动力学、空间约束对于畴结构演化的影响规律及畴结构有序化调控。项目基本按照立项思路，针对诱导锰氧化物反铁磁相的关键应变因素和八面体畸变类型进行深入研究，并揭示环状结构畴壁限域的反铁磁相演化和准周期重现的动力学。. 项目总体执行情况良好。（1）利用单轴张应变工程调控锰氧化物外延膜基态，进而利用弯曲应变可逆动态的操控反铁磁绝缘相强度，结合高分辨透射电镜和密度泛函理论计算证实新奇反铁磁相与薄膜的b轴张应变关联，并指出Q2模式的八面体畸变和电荷有序扮演着重要作用，成果以“Uniaxial strain-controlled ground states in manganite films”为题发表在《Nano Letters》杂志上。（2）在多参量优化调控的反铁磁相体积分数占主导的锰氧化物外延单晶膜中，发现结构起源的环状铁磁金属畴壁对反铁磁相演化动力学具有限域作用，且反铁磁相重现呈准周期特征，成果以“Induced formation of structural domain walls and their confinement on phase dynamics in strained manganite thin films”为题发表在《Advanced Materials》杂志上。所涉及的研究内容都取得了进展，共发表包括Nature Materials，Nano Letters，Advanced Materials等高水平期刊论文12篇。