[Pt/FM]n/MgO基垂直磁各向异性纳米线中电流诱导畴壁运动的物理机制研究

Since the discovery of current-induced magnetic domain walls (DWs) motion in magnetic nanowires, the nano-devices designed around DWs motion have become one of hot topics in spintronics recently. The nanowires with perpendicular magnetic anisotropy (PMA) are the most promising applied in future ultra-high density storage or logic devices due to their lower critical current density of DWs motion compared with in-plane magnetized nanowires. This project intends to research the physical laws and mechanisms of magnetic DWs motion under pulse current in the [Pt/FM]n/MgO based composite structure multilayer nanowires with PMA patterned by electron beam lithography. The emphasis is to understand the influences of the interface exchange coupling in multilayers on the critical current density and DWs’ pinning characteristics controlled by electric field to effectively reduce the critical current density of DWs motion through tuning the interfacial properties of FM/Pt and FM/MgO interfaces. The work has great guide meaning and application value in the development of magnetic DWs-based nano-devices.

电流诱导磁性纳米线中畴壁运动这一现象的发现使得围绕磁畴壁运动而设计的纳米器件成为近年来自旋电子学的研究热点之一。垂直磁各向异性纳米线其畴壁移动的临界电流密度远低于传统的面内磁化纳米线，最有希望在未来超高密度存储或逻辑器件中得到应用。本课题拟采用电子束曝光技术制备具有垂直磁各向异性的[Pt/FM]n/MgO基复合结构多层膜纳米线，研究其在脉冲电流作用下磁畴壁的运动规律以及物理机制。重点研究多层膜界面交换耦合对纳米线中畴壁移动的临界电流密度和局域电场作用下磁畴壁的钉扎特性的影响。通过调控FM/Pt、FM/MgO的界面特性有效地降低畴壁移动的临界电流密度。本研究开展对于磁畴壁基纳米器件的开发具有重要的指导意义和应用价值。

近年来，磁畴壁运动以其丰富的物理内涵和潜在的应用前景，成为自旋电子学领域的研究热点之一。除了铁磁材料中电流诱导的自旋转矩效应外，铁磁/非磁界面的Rashba效应和自旋力矩也会对薄膜磁性、畴壁运动产生重要影响。本项目围绕[Pt/FM]n/MgO结构的垂直磁各向异性、电场调控及自旋输运特性进行了系统的研究。此外还对Pt/FM界面的自旋轨道矩、磁性绝缘体薄膜中自旋塞贝克效应、自旋霍尔磁电阻效应、磁振子输运等展开研究。成功制备了具有垂直磁各向异性半金属多层膜Pt/Co2FeAl0.5Si0.5/MgO、Pt/Co2FeAl0.5Si0.5/MgAl2O4，并对其磁性进行了优化，这种垂直磁各向异性的半金属材料可以应用于隧道结器件中，具有理论上很高的隧穿磁电阻，同时具有低的磁畴壁移动的临界电流密度；在Pt/Co2FeAl0.5Si0.5/MgO结构中，实现了电场对薄膜垂直磁各向异性的有效调控；对Ta/CoFeB/MgAl2O4结构中反常霍尔效应的物理机制与磁各向异性内在联系进行了揭示；在YIG/Pt非局域结构中，首次利用DC模式电学方法分离了自旋塞贝克效应和磁振子磁电阻效应。研究成果将有利于加深对磁畴壁和磁振子作为信息载体，其输运行为的理解。