磁性绝缘体/非磁金属异质结的磁电阻效应研究

The pure spin current can be transport in magnetic insulator by the spin wave. Owing to the absence of the conductive electrons in magnetic insulator, there is no current and corresponding Joule heating. Therefore, it is possible to significantly reduce the power consumption in the electronic devices based on magnetic insulator. Moreover, several new phenomena and effects related with pure spin current are discovered in magnetic insulator, such as spin Seebeck effect and spin pumping effect. Owing to the strong potential applications and the novel phenomena, the spin transport in magnetic insulator has been one of the new frontiers in spintronics. In all of these studies, the magnetic insulator/non-magnetic metal heterostructure is the fundamental sample structure. In this project, we focus on studying the magnetoresistance effect in Y3Fe5O12/non-magnetic metal heterostructure. Firstly, we will investigate the influence of the extrinsic effects such as the roughness on the magnetoresistance effect. The correlation of the Y3Fe5O12 magnetization and the magnetoresistance, the impact of the metal interface on the pure spin transport and the corresponding magnetoresistance effect will be systematically studied. In addition, we will try to explore the magnetoresistance effect on different magnetic insulators. These studies can not only reveal the mechanisms of the magnetoresistance effect in these systems, but also be useful for understanding the spin current transport in magnetic insulator.

磁性绝缘体可以以自旋波的形式输运纯自旋流，由于绝缘体没有导电电子，也就不会产生电流和焦耳热，因此基于磁性绝缘体的自旋电子器件可以极大的降低功耗。另外磁学绝缘体中还发现了许多新的与纯自旋流输运相关的物理现象和效应，如自旋塞贝克效应和自旋泵浦效应等。这些潜在的应用和新奇的物理现象使得磁性绝缘体的自旋输运成为了自旋电子学研究的前沿热点之一。在这些研究中磁性绝缘体/非磁金属异质结是最基本的样品结构，本项目主要研究Y3Fe5O12/非磁金属异质结的磁电阻效应。拟首先研究并排除界面粗糙度等非本征因素对磁电阻的影响，然后系统研究Y3Fe5O12的磁性与磁电阻的关联，金属界面对纯自旋流的作用和磁电阻效应的影响。另外还研究其它磁性绝缘体/非磁金属异质结体系的磁电阻效应。这些研究不仅可以揭示这类体系磁电阻的物理机制，而且也有助于理解与磁性绝缘体相关的其它自旋流输运现象。

磁性绝缘体和非磁金属构成的异质结可以产生磁电阻效应，被称为自旋霍尔磁电阻(SMR)的效应，该效应与自旋霍尔效应和自旋在界面的传输相关，因此，通过SMR可以帮助理解自旋在非磁金属中产生的机制和自旋在界面传输的机理。申请人研究了Pt/Y3Fe5O12 (Pt/YIG)界面的状态，发现界面在Pt/YIG界面存在电荷转移和界面互扩散，这对自旋在界面的传输有重要影响。进一步通过调节Pt在YIG表面的覆盖度，发现源于界面Rashba效应的新型磁电阻效应。发现在Pt上覆盖自旋霍尔角相反W，W在一定厚度下SMR增大，表明自旋积累增强。申请人还利用SMR实现的微波的整流效应。在垂直各向异性的Tm3Fe5O12和Pt的异质体系中验证了存在Dzyaloshinskii-Moriya相互作用(DMI)。另外，纠正了高分子具有和金属Pt相当的自旋-电荷转化效率的观点。基于Pt/NiO双层膜，用激光激发，室温零磁场获得了约1皮秒脉冲宽度的纯自旋流。这些结果帮助人们理解了自旋在金属中的调控，在界面传输的机制，促进了利用自旋流实现低功耗的器件。