Quantifying Spin-Orbit Coupling in Rare-Earth Metals via Inverse Spin Hall Effect

非技术描述：稀土金属和合金是对社会产生重大影响的几种技术的战略重要材料，包括电动和混合动力汽车、永磁体、催化剂、节能照明和激光。稀土的独特特性源于其电子结构和性质。了解稀土金属中的这些特殊方面可以为未来基于稀土材料的变革性技术提供指导。此外，钇铁石榴石（YIG）是一种重要的磁性材料，广泛应用于微波应用，如电信和雷达技术，以及近年来的自旋泵浦。在首席研究员的团队中，具有最先进质量的YIG薄膜提高了自旋泵浦效率，从而提高了纯自旋输运设备未来应用的可能性。生产高质量材料的能力对于提高美国的全球竞争力至关重要。该项目还包括努力提高科学、技术、工程和数学领域的多样性，包括：在俄亥俄州立大学的美国物理学会桥梁项目中为一名未被充分代表的少数族裔学生提供建议，促进不同群体的研究生和本科生参与尖端研究，并为当地一所高中建立超导磁悬浮实验，以鼓励年轻学生在STEM领域寻求职业发展。技术描述：本研究项目的目标是研究镧系稀土金属中的逆自旋霍尔效应和自旋轨道耦合，并了解自旋霍尔物理在这组从根本上有趣且技术上重要的材料中的系统行为。自旋电子学领域的一个主要焦点是追求以自旋霍尔角为特征的具有大自旋霍尔效应的材料。这导致了广泛材料中自旋霍尔角的定量测定，包括主要研究者对3d和5d过渡金属的系统测量。s组。事实上，过渡金属表现出一些最大的自旋霍尔角，由于d电子的大轨道矩，这表明有可能在稀土金属中发现更大的自旋霍尔效应，因为它们具有巨大的f轨道矩和理论预测的大原子序数。然而，迄今为止，稀土金属中的自旋霍尔效应基本上尚未被探索。从YIG薄膜中抽取纯自旋电流的铁磁共振自旋泵入金属是表征逆自旋霍尔效应和提取自旋霍尔角的一种通用而可靠的技术。本项目的目标是：(1)了解纯镧系稀土金属中固有的逆自旋霍尔效应，揭示4f电子在自旋霍尔效应中的作用；(2)研究了铜和金中稀土杂质引起的外源逆自旋霍尔效应；(3)表征稀土金属与其他材料之间的界面自旋电导，了解界面间的自旋传递效率。本研究的预期结果是对稀土金属中自旋霍尔物理的系统和定量的认识，稀土金属原则上具有出现超大自旋霍尔效应的所有属性。

Non-technical description:Rare earth metals and alloys are strategically important materials for several technologies that have significantly impacted society, including electric and hybrid vehicles, permanent magnets, catalysts, energy-efficient lightings, and lasers. The unique characteristics of rare earths arise from their electronic structure and properties. Understanding special aspects of these in rare-earth metals can provide guidance for future transformative technologies based on rare-earth materials. In addition, yttrium iron garnet (YIG) is an important magnetic material widely used in microwave applications such as telecommunication and radar technologies, and recently in spin pumping. The YIG films with state-of-the-art quality grown in the principal investigator's group improve the spin pumping efficiency and therefore the probability for future application of pure spin transport devices. The ability to produce top-quality materials is essential for enhancing the global competitiveness of the United States. This project also includes an effort toward improving diversity in Science, Technology, Engineering and Mathematics fields, including: advising an underrepresented minority student in the American Physical Society Bridge Program at the Ohio State University, promoting participation of a diverse group of graduate and undergraduate students in cutting-edge research, and building superconductor magnetic levitation experiments for a local high school in encouraging young students to pursue a career in the STEM fields.Technical description:The objective of this research project is to investigate the inverse spin Hall effect and spin-orbit coupling in the lanthanide rare-earth metals and understand the systematic behavior of spin Hall physics in this group of fundamentally intriguing and technologically important materials. One major focus of the spintronics field is the pursuit of materials with large spin Hall effect as characterized by the spin Hall angle. This has led to quantitative determination of spin Hall angles in a broad range of materials, including the systematic measurements on the 3d and 5d transition metals by the principle investigator?s group. In fact, transition metals exhibits some of the largest spin Hall angles due to the large orbital moment of the d electrons, which points toward the possibility of finding even larger spin Hall effect in rare-earth metals due to their giant f-orbital moments and large atomic numbers as predicted by theory. However, the spin Hall effect in rare-earth metals is essentially unexplored to date. Ferromagnetic resonance spin pumping of pure spin currents from YIG thin films into metals is a versatile and reliable technique for characterizing the inverse spin Hall effect and extracting spin Hall angle. This project has the following goals: (1) understand the intrinsic inverse spin Hall effect in pure lanthanide rare-earth metals and uncover the role of 4f electrons in spin Hall effect; (2) investigate the extrinsic inverse spin Hall effect arising from rare-earth impurities in copper and gold; (3) characterize the interfacial spin conductances between the rare earth metals and other materials to understand spin transfer efficiency across interfaces. The expected outcome of this research is the systematic and quantitative understanding of the spin Hall physics in rare earth metals, which, in principle, possess all the attributes for the emergence of exceptionally large spin Hall effect.