庞磁电阻钙钛矿氧化物人工微结构中的自旋调控、外延应变及磁性研究

Perovskite oxide superlattice films have been widely used as the candidate material for many novel spintronic materials and devices due to their multi-functionality and mutual control of various functions. This project is based on the Magnetic Hamiltonian theory of Metallic oxide. We regard the design and growth of artificial microstructure of perovskite oxides as the starting point of our research. The interface electron spin and the epitaxial strain in our superlattice will be modulated by altering the superlattice period, the thickness of each component, the total thickness as well as the type and orientation of the substrate. The study will elaborate the regular patterns and physical mechanism that the interface electrons spin displays in controlling the material’s magnetic structure and magnetic effect. We will do research on the effective way that the interface spin frustration controls the magnetic properties and the colossal magnetoresistance effect and on their associated nature. The physical model through which spin frustration enhances the magnetoresistance effect will be set up so as to improve the colossal magnetoresistance effect. Our research will master the rules about how the epitaxial strain influences the magnetic structure, the magnetic effect and the interface spin order. The project aims to deepen our understanding of the physical nature of the relationship between structure and property in perovskite artificial microstructure, enrich and develop basic theories about correlated electron system’s spin modulation and the epitaxial strain effect in order to provide theoretical and experimental guidance for the design of the newly-typed multifunctional magnetic materials and devices.

钙钛矿氧化物超晶格薄膜因具有多功能性而且可实现多种功能间的相互调控而成为多种新型自旋电子学材料及器件的候选材料。本项目以金属氧化物磁性哈密顿理论为理论依据，以钙钛矿氧化物人工微结构的理论设计和探索合成为起点，通过改变超晶格周期、各组分的厚度、总厚度、衬底类型和取向实现对超晶格界面电子自旋和外延应变的调制，精确的控制薄膜的取向和应变可以有效控制薄膜的微观结构、磁结构和磁性能，阐明界面电子自旋相对取向在调控材料磁结构和磁效应中的作用规律及物理机制。重点关注分析界面电子自旋取向、自旋失措和取向相关的外延应变对体系磁结构、磁效应和磁电阻效应的影响规律，阐明内在的物理机制和关联本质，提高体系的磁电阻效应，丰富和发展关联电子体系自旋调控和外延应变方面的基础理论，从而为多功能新型磁电子学材料及器件的设计提供理论和实验指导。

作为新型自旋电子学材料及器件的候选材料，本项目以LaMnO3、SrMnO3、La0.67Sr0.33MnO3、LaFeO3等几种钙钛矿氧化物薄膜及其异质结构为研究对象，围绕薄膜异质结构的理论设计和探索合成、人工微结构优化调控材料微结构和磁、电功能特性的有效途径和物理机制等方面开展研究工作。本项目利用脉冲激光沉积技术和射频磁控溅射技术，探索了氧分压、O2/Ar流量比、衬底温度、靶材-衬底距离、激光能量密度、激光频率、溅射时间等工艺参数对LaMnO3、SrMnO3、La0.67Sr0.33MnO3等薄膜生长模式和成膜质量的影响，获得了RHEED振荡曲线清晰可见、在原子尺度上可精确控制的单层及多层薄膜，阐明了镀膜过程中O2/Ar流量比与薄膜中铁磁/反铁磁共存和竞争和宏观磁性特征演变之间的物理机制，揭示了外延应变对La0.67Sr0.33MnO3外延薄膜磁性和输运性质的调控机制，探讨了LaMnO3/SrMnO3超晶格、La0.67Sr0.33MnO3/LaFeO3双层膜、SrMnO3/LaFeO3超晶格等人工微结构的周期、各组分相对厚度、总厚度和应变状态等对薄膜磁结构、磁效应、输运性质和磁电阻效应的作用机理，初步实现了人工微结构设计对薄膜磁电功能特性的有效调控。此外，还研究了不同类型氧化物半导体异质结构界面的光生载流子迁移行为及其对材料光电化学性质影响的物理机制。本项目研究为探索多功能新型磁电子学材料及器件的应用提供了理论和实验支持。