Collaborative Research: Spin Currents and Spin-orbit Torques in Single Layer Magnetic Systems

合作研究：单层磁系统中的自旋电流和自旋轨道扭矩

• 批准号: 2105218
• 负责人: Xin Fan
• 金额: $ 30.28万
• 依托单位: University of Denver
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-06-01 至 2025-05-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2105218&HistoricalAwards=false
• 关键词: Collaborative; Research; Spin; Currents; orbit

Non-technical AbstractFerromagnetic materials are widely used in digital information storage devices such as hard disk drives, which boast long-term memory, high storage density, and cost-effectiveness. Compared to other semiconductor-based memory devices, the operation speed of hard disk drives is relatively slow, prompting the development of magnetic memories without moving parts. To make such memory technologies competitive requires efficient control of magnetism using electrical currents rather than magnetic fields. In recent years, a novel mechanism called spin-orbit torque has been shown to electrically control magnetism in both ferromagnetic and antiferromagnetic materials—the latter of which are far more prevalent in nature but currently underutilized, despite offering several advantages over their ferromagnetic cousins like potentially higher speed and density. However, the spin-orbit torques generated in multilayer magnetic systems arise from several competing mechanisms that are difficult to disentangle, widening the gap between experiment and theory and preventing device optimization. This collaborative project aims to determine the microscopic origins and behavior of spin-orbit torques generated within single ferromagnetic and antiferromagnetic layers using both theoretical and experimental methods. Success in this research will help optimize spin-orbit torques, thus expediting the development of faster magnetic memory devices used for traditional information storage and for artificial intelligence applications. This project trains graduate and undergraduate students in a variety of research techniques and prepares them for the workforce in science and technology. Planned outreach activities include establishing an online seminar series inviting researchers from underrepresented groups in physics and engineering to give talks combining their frontier research with their personal experience in pursuit of their scientific career.Technical AbstractAchieving efficient electrical control of magnetic order is crucial for the development of memory technology. Spin-orbit torque—which is a transfer of angular momentum from the atomic lattice of crystals to magnetic order under an applied electric field—promises faster, more reliable, and more energy-efficient switching than previous write mechanisms in magnetic memories. While control of magnetism using spin-orbit torque has been demonstrated in various devices, the role of the ferromagnetic and antiferromagnetic layers in generating spin-orbit torques remains unclear, creating inconsistencies between experiment and theory and preventing device optimization. This collaborative project experimentally and theoretically characterizes boundary spin-orbit torques generated within single-layer magnetic materials, eliminating competing mechanisms from adjacent layers. The single-layer magnetic systems include ferromagnets, non-collinear and collinear antiferromagnets. The boundary spin-orbit torques are measured using the magneto-optic-Kerr-effect and the results are theoretically interpreted using both semiclassical models and the first-principles transport calculations. This collaborative research aims to disentangle the spin torque contributions that must also occur in multilayers while paving the way for single layer magnetic memories. It also undertakes the first characterization of spin torques in single antiferromagnetic layers with non-collinear and collinear magnetic order, broadening the role of antiferromagnets in spin-orbit coupled nanostructures. This project trains graduate and undergraduate students in a variety of research techniques such as thin film growth, micro-fabrication, optical detection, first-principles calculations, and semiclassical modeling, preparing them for the workforce in science and technology.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

非技术抽象的Ferromagnetic材料被广泛用于数字信息存储设备，例如硬盘驱动器，这些磁盘驱动器的长期记忆，高存储密度和成本效益。与其他基于半导体的内存设备相比，硬盘驱动器的操作速度相对较慢，促使磁性记忆的发展而没有运动部件。为了使这种记忆技术竞争需要有效地使用电流而不是磁场来控制磁力。近年来，已经显示出一种称为自旋轨道扭矩的新型机制可以在铁磁和抗铁磁材料中电气控制磁性，后者在本质上更为普遍，但目前未充分利用，优先于其超级磁性表皮，例如潜在的更高的速度和密度。但是，多层磁系统中产生的自旋轨道扭矩是由难以解开的几种竞争机制引起的，从而扩大了实验和理论之间的差距，并防止了设备优化。该协作项目旨在确定使用理论和实验方法在单个铁磁和反铁磁层中产生的自旋轨道扭矩的微观起源和行为。这项研究的成功将有助于优化自旋轨道扭矩，从而加快用于传统信息存储和人工智能应用程序的更快的磁性存储设备的开发。该项目通过各种研究技术培训毕业生和本科生，并为科学技术的劳动力做好准备。计划中的外展活动包括建立一个在线半段系列系列，邀请来自代表性不足的物理和工程团体的研究人员进行谈判，将他们的边界研究与他们的个人经验相结合，以追求他们的科学职业。自旋轨道扭矩（这是角动量从晶体的原子晶格转移到施加的电场下的磁顺序），比磁性记忆中先前的写入机制更快，更可靠，更可靠，更节能的开关。尽管在各种设备中都证明了使用自旋轨道扭矩对磁性的控制，但铁磁和抗铁磁层在产生自旋轨道扭矩中的作用尚不清楚，在实验和理论之间产生不一致并防止设备优化。该协作项目在实验和理论上表征了在单层磁性材料中生成的边界自旋轨道扭矩，从而消除了来自相邻层的竞争机制。单层磁系统包括铁磁性，非共线和共线抗铁磁铁。边界自旋轨道扭矩是使用磁极 - 凯尔效应测量的，结果是使用半经典模型和第一原理传输计算来解释的。这项协作研究旨在解散多层中必须发生的自旋扭矩贡献，同时为单层磁性记忆铺平道路。它还在单个抗铁磁层中首次表征自旋扭矩，具有非连续性和共线磁性，扩大了抗铁磁体在自旋轨道耦合纳米结构中的作用。该项目通过各种研究技术培训毕业生和本科生，例如薄膜的增长，微型制作，光学检测，第一原理计算和半经典模型，为科学和技术的劳动力做准备。该奖项奖通过评估NSF的法定任务，并通过评估了基金会的范围，并反映了NSF的法定任务，并已被认为是基金会的范围。

项目成果

Influence of non-uniform magnetization perturbation on spin-orbit torque measurements

非均匀磁化扰动对自旋轨道扭矩测量的影响

• DOI: 10.1016/j.jmmm.2022.169877
• 发表时间: 2022
• 期刊: Journal of Magnetism and Magnetic Materials
• 影响因子: 2.7
• 作者: Greening, Ryan W.;Fan, Xin
• 通讯作者: Fan, Xin