Spin-orbit Interaction Driven Phenomena in Magnetic Heterostructures

非技术摘要最近在自旋电子学领域的突破，科学家们除了探索电子的电学性质外，还探索了自旋或磁性，为未来几代存储和逻辑器件创造了机会。研究发现，电流通过铂或钽等重金属，可以在横向上产生纯自旋电流，其中具有相反自旋方向的电子以相反的方向运动。这种纯粹的自旋电流扩散到邻近的磁层中，并对磁层中的自旋施加扭矩，导致了控制磁层性质的有效方法。该项目旨在从根本上了解纯自旋电流如何穿过材料和界面，并与磁层中的自旋相互作用。通过对人工制品免疫的实验检测方法中的新方法以及界面工程，研究团队可以分离和量化由整体和界面效应产生的各种贡献。这项研究还可能带来对纳米磁体提供更有效控制的新材料，纳米磁体是存储器和逻辑器件的关键成分。该项目利用特拉华大学纳米制造设施的创建，还旨在通过纳米制造课程和认证计划培训本科生和研究生和专业人员。教育活动还包括以K-12学生为重点的外展计划。技术摘要自旋-轨道相互作用(SOC)驱动的电流诱导磁化转换和磁畴运动等现象引起了人们的极大关注。这些现象是由自旋霍尔效应(SHE)、界面Rashba SOC和Dzyaloshinskii-Moriya相互作用(DMI)等效应的复杂组合引起的，这些效应与材料和界面上的SOC密切相关。为了释放铁磁异质结构在自旋电子学应用中的真正潜力，了解导致铁磁异质结构这些令人兴奋的发现的潜在物理基础是至关重要的。目前还缺乏能够解开She和Rashba效应带来的扭矩纠缠的实验技术。通过设计对自旋电流几乎透明但显著修改Rashba效应的界面，以及创新的3D MOKE自旋扭矩磁强计(可以测量任意方向上的磁化扭矩)，该研究提出了一项全面的实验努力，以了解这些铁磁异质结构中丰富的SOC驱动现象。该项目的目标是：(1)开发能够以任意角度测量SO磁化扭矩的3D MOKE自旋扭矩磁强计；(2)定量分离SHE和Rashba SOC对SO扭矩的贡献，并将它们与界面SOC相关联；(3)表征和优化DMI，特别是在具有大的压控界面磁各向异性的结构中；以及(4)寻找具有较好的SOC诱导效应的新材料系统。

Nontechnical AbstractRecent breakthroughs in the field of spintronics, where scientists explore the spin or magnetic properties in addition to the electric properties of electrons, have created opportunities for future generations of memory and logic devices. It is found that an electrical current passing through a heavy metal such as platinum or tantalum can create, in the traverse direction, a pure spin current where electrons of opposite spin directions move in opposite directions. This pure spin current diffuses into a neighboring magnetic layer and exerts torque on spins in the magnetic layer, leading to an effective method of controlling the properties of the magnetic layer. The project aims towards acquiring a fundamental understanding of how a pure spin current traverses through materials and interfaces and interacts with spins in the magnetic layer. With novel approaches in experimental detection methods that are immune to artifacts and with interface engineering, the research team can separate and quantify various contributions arising from the bulk and interface effects. The research may also lead to new materials that provide more efficient control over nano-magnets, key ingredients in memory and logic devices. The project, leveraging on the creation of a nanofabrication facility at the University of Delaware, also aims to train undergraduate and graduate students and professionals via nanofabrication courses and certification programs. The educational activities also include outreach programs focusing on K-12 students. Technical AbstractSpin-orbit interaction (SOC) driven phenomena, such as current-induced magnetization switching and domain motion in magnetic heterostructures involving heavy metals, have attracted great attention. These phenomena arise from an intricate combination of effects including the Spin Hall Effect (SHE), interfacial Rashba SOC, and Dzyaloshinskii-Moriya Interaction (DMI), which are strongly correlated with SOC in materials and at interfaces. It is essential to understand the underlying physics responsible for these recent exciting discoveries in ferromagnetic heterostructures in order to unleash their true potential in spintronic applications. There is a lack of experimental techniques that can unravel the entanglement of torques from the SHE and Rashba effect. With designed interfaces that are nearly transparent to spin currents but significantly modify the Rashba effect and innovative 3D MOKE spin torque magnetometers that can measure torques on magnetization at arbitrary directions, the research proposes a comprehensive experimental effort to understand the rich SOC-driven phenomena in these ferromagnetic heterostructures. The project objectives are to: (1) develop 3D MOKE spin torque magnetometers capable of measuring SO torques on magnetization at an arbitrary angle, (2) quantitatively separate the SHE and Rashba SOC contributions to the SO torques, and relate them to the interface SOC, (3) characterize and optimize DMI, particularly in structures with large voltage controlled interface magnetic anisotropy, and (4) search for new material systems that possess preferred SOC-induced effects.