Spin Transport in Metals and Oxides

非技术描述：材料的薄层或薄膜中的磁性以及多层之间的界面处的磁性多年来一直引起人们的注意。这是由于基本的科学兴趣，但也是技术上的重要性，因为磁性薄膜使现在为云存储提供动力的硬盘驱动器等设备成为可能。尽管这种“自旋电子”技术已经成熟，但人们对这类材料的理解仍然存在令人惊讶的差距，下一代设备也面临着重大障碍。一个例子是，通过在磁性金属的界面上注入电子，可以在其他非磁性金属中感应磁性。这被称为“自旋注入”，电子随后的运动使得“自旋输运”成为可能。尽管工作中的技术依赖于这些效应，但许多基本问题仍然没有答案，包括是什么限制了注入的自旋流可以持续多远。这个项目的目标是准确地理解这一点，专注于材料中不完美的最重要的作用。除了阐明鲜为人知的基本物理学外，这也有助于下一代硬盘驱动器读取头的发展。该项目不仅在传统磁性金属上做到了这一点，而且在导电氧化物材料的新领域也做到了这一点。除了在科学和技术方面的影响外，这些活动还培养活跃的跨学科研究领域的本科生和研究生，直接为美国的熟练劳动力做出贡献。主要是通过首席研究人员开发的一项教育计划，每年可影响多达500名学生。技术描述：该项目使用纳米级横向非局部自旋阀实现电荷和自旋流的分离，以显著提高对金属和氧化物中自旋注入和松弛的理解。其目标是对限制非磁性金属和氧化物中自旋扩散长度和寿命的因素有一个普遍的物理理解，从而直接有助于探索用于下一代硬盘驱动器读取头的低阻面积产品传感器技术。在这项工作中，引起非磁性金属自旋弛豫的因素被系统地解卷积，提供了对磁性杂质、自旋轨道散射中心、晶界、表面、界面和声子的作用的充分理解。这项研究还包括一些新颖的实验，旨在了解局部磁矩、近藤物理，甚至磁相互作用和涨落对含有磁性杂质的金属中自旋输运的作用。这项工作将逐步从传统金属转移到导电氧化物，探索高度自旋极化的复杂氧化物自旋注入器提供的机会，了解氧化物金属中自旋注入、扩散和弛豫的基本原理的前景，以及将自旋输运与电子相变相结合的迷人新物理学的潜力。

Non-technical description:Magnetism in thin layers or films of materials, and at interfaces between multiple layers, has attracted attention for many years. This is due to basic scientific interest, but also technological importance, as magnetic films enable such devices as the hard disk drives that now power cloud storage. Despite the maturity of such "spintronic" technologies there remain surprising gaps in the understanding of such materials, as well as major obstacles to next generation devices. One example is the manner in which magnetism can be induced in otherwise non-magnetic metals by injecting electrons across an interface with a magnetic metal. This is termed "spin injection", the subsequent motion of the electrons enabling "spin transport". Despite the fact that working technologies rely upon these effects, many fundamental questions remain unanswered, including what limits how far injected spin currents can persist. The goal of this project is to understand exactly this, focusing on the all-important role of imperfections in the materials. In addition to elucidating the poorly understood basic physics, this also contributes to the development of next generation hard drive read heads. This project does this not only with conventional magnetic metals, but also in the new realm of conductive oxide materials. In addition to impact in both science and technology, these activities train undergraduate and graduate students in an active, interdisciplinary research field, directly contributing to a skilled US workforce. Outreach to the public is also achieved, primarily through an educational program developed by the principal investigator that can impact up to 500 school students a year.Technical description:This project uses the separation of charge and spin currents enabled by the nanoscopic lateral non-local spin valve to dramatically improve the understanding of spin injection and relaxation in metals and oxides. The goal is to develop a general physical understanding of the factors that limit spin diffusion lengths and lifetimes in non-magnetic metals and oxides, thus directly contributing to the exploration of low resistance-area product sensor technologies for next generation hard disk drive read heads. The factors inducing spin relaxation in non-magnetic metals are being systematically deconvoluted in this work, providing a full understanding of the role of magnetic impurities, spin-orbit scattering centers, grain boundaries, surfaces, interfaces, and phonons. The research additionally includes novel experiments aimed at understanding the role of local magnetic moments, Kondo physics, and even magnetic interactions and fluctuations on spin transport in metals with magnetic impurities. The work will gradually move from conventional metals to conductive oxides, exploring the opportunities provided by highly spin polarized complex oxide spin injectors, the prospects to understand the fundamentals of spin injection, diffusion and relaxation in oxide metals, and the potential for fascinating new physics combining spin transport with electronic phase transitions.