钙钛矿型钴氧化物应变超薄膜的局域结构和自旋-轨道秩序的掠入射荧光XAFS研究

项目名称： 钙钛矿型钴氧化物应变超薄膜的局域结构和自旋-轨道秩序的掠入射荧光XAFS研究

项目编号： No.U1232110

项目类型： 联合基金项目

立项/批准年度： 2013

项目学科： 物理学II

项目作者： 郑金成

作者单位： 厦门大学

项目金额： 60万元

中文摘要： 过渡金属氧化物由于系统内部自旋、轨道、电荷多自由度的强烈耦合而呈现出许多奇异性质，从而成为凝聚态物理领域研究的热点之一。具有钙钛矿结构的钴氧化物LaCoO3在一定的应变条件下从非磁性到铁磁性的反常磁相变引起了广泛的关注，但机理还不太明确。此外，该氧化物有望应用于高温的热电器件中，然而其热电理论还有待深入研究。本项目拟在氧化物衬底上沉积厚度为10-100nm 尺度范围的LaCoO3 钴氧化物超薄膜，通过挑选具有不同晶格常数的金属氧化物衬底来调制薄膜的应变，并利用掠入射荧光X 射线吸收精细结构（XAFS）技术，结合其他辅助表征手段，研究钙钛矿型钴氧化物超薄膜的局域结构和自旋-轨道秩序，并对其热电性能进行测量。本项目的意义在于理清钴氧化物在应变场下的微观结构和电子性质变化的图像，探索多局域效应及其协同作用对钴氧化物的热电性质的影响，有望为提高钴氧化物的热电转换效率提供设计指南。

中文关键词： XAFS；钴氧化物；热电；热导率；纳米能源材料

英文摘要： Transition-metal oxides become one of the hot research topics in condensed matter physics because of their exotic physical properties, due to the strong coupling between their spin, orbital, and charge. Particularly, the perovskite cobalt oxide LaCoO3 shows unusual nonmagnetic - ferromagnetic transition under certain strained conditions, which attracts lot of interests. But their origins are still not clear. In addition, cobalt oxides are promising materials for various applications, such as high temperature thermoelectric devices. However, the related thermoelectric theory is not yet matured. In this project, we propose to synthesize LaCoO3 films with thickness in the range of 10-100 nm, and tune the strain of the films using substrates with different lattice constants. We will then use grazing incidence fluorescence XAFS to study local structures and spin-orbital orders of the strained perovskite cobalt oxide films, and characterize their thermoelectric properties. This project will paint a clear picture of microstructure and electronic properties of cobalt oxide films under strains, study the effects of various local fields on thermoelectric properties of the cobalt oxides, and provide some guidelines for improving their thermoelectric conversion efficiency.

英文关键词： XAFS；Cobalt oxide；Thermoelectric；Thermal conductivity；Nano energy materials