有序氧空位对钙钛矿类过渡金属氧化物磁、电性质影响的研究

As the topochemical reduction and electron beam induced methods become mature technologies, precise controlling the arrangement and concentration of atoms and vacancies has become an important method in atomic scale. In perovskite-type transition metal oxides, the existed oxygen vacancies can break the inversion of symmetry and at the same time can server as efficacious doping of current carrier. Thus it can control the magnetic and electric properties, moreover, create novel properties which their bulk materials do not have. For this propose, in this project, based on first principles method, the effect on the magnetic and electric properties affected by the oxygen vacancies of the perovskite oxygen compounds will be systematically studied, including: (1) the effect of the oxygen vacancies on the lattice and electric structure; (2) the ferroelectric and multiferroic induced by the oxygen vacancies; (3) the effect of oxygen vacancies on the surface charge of the nanoscale ferroelectric perovskite compounds. By the investigation in the project, it is tended to build the regulated relationship between the oxygen vacancies and charge, spin, or orbital ordered; open a new way which can induce ferroelectricity and though coordinating the coexisted condition between the ferroelectric and magnetic, enhance the coupling between the ferroelectricity and magnetism; reveal the regulation between the surface charge and the oxygen vacancies in thin ferroelectric perovskite films, and supply theoretical guidance for designing ferroelectric and multiferroic materials in nanoscale.

随着局部化学还原和电子束诱导等技术的日趋成熟，在原子尺度上精准操控原子和空位的排列方式已经成为材料改性的一种重要手段。在钙钛矿类过渡金属氧化物中，由于氧空位破坏局部空间反演对称性并同时提供有效的载流子掺杂，可以极大的调控其磁、电性质，更可以导致完整晶体材料中所不具备的新颖物性。为此，本项目采用第一性原理计算方法系统研究有序氧空位对钙钛矿氧化物材料的磁、电性质的影响，研究内容包括：（1）氧空位对钙钛矿类过渡金属氧化物晶格和电子结构的影响；（2）氧空位诱导的铁电性和多铁性；（3）氧空位在纳米尺度上对铁电钙钛矿氧化物表面电荷的影响。通过本项目的实施，探索氧空位与电荷序、自旋序和轨道序之间的调制机制；提出新的铁电性诱导机理，通过协调材料中铁电性和磁性的共存条件，增强铁电性和磁性之间的耦合；揭示氧空位与薄膜铁电材料表面电荷的调控机制，为设计纳米尺度的铁电和多铁材料及其实际应用提供理论指导。

钙钛矿材料因其具有丰富的磁学和电学物理性质，而成为研究的热点材料之一。研究如何调控钙钛矿材料的磁、电性质成为近年来的热门课题。通过研究研究应力、晶格、电荷和氧空位之间的相互调制关系，不仅可以改善材料的磁、电性质，更可以制备出多功能的铁磁，铁电和多铁材料。本项目采用第一性原理研究了应力对钙钛矿材料结构变化和电子结构的影响，外加的应力可以在非铁电材料中诱导出铁电性；结合实验中的发现，研究了钙钛矿材料的磁结构、电子结构、轨道和晶格之间的相互调制作用，发现了新型的三维轨道序和电荷序，电荷序的出现可以使铁电和铁磁性出现在单相材料中，为多铁材料的研究提供了理论的指导；研究了氧空位对钙钛矿材料电子结构、磁性和应力之间的调制关系，发现了氧空位的出现对体系的晶体结构，输运性质和磁结构都有相关的调制作用，为实验中研究钙钛矿材料的物性调控提供理论的指导。取得了项目所期望的一系列结果。