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

非技术描述：稀土金属和合金是几种对社会产生重大影响的技术的重要战略材料，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它们的电子结构和性质。了解稀土金属中这些方面的特殊方面，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，广泛应用于通信、雷达等微波领域，最近还被用于自旋泵浦。主要研究组生长的YIG薄膜具有最先进的质量，提高了自旋泵浦效率，从而提高了未来应用纯自旋输运器件的可能性。生产高质量材料的能力对于增强美国的全球竞争力至关重要。该项目还包括改善科学、技术、工程和数学领域的多样性的努力，包括：为俄亥俄州立大学美国物理学会桥梁计划中代表性不足的少数族裔学生提供建议，促进不同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领域从事职业。技术描述：本研究项目的目标是研究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基本有趣和具有技术重要性的材料中的系统行为。自旋电子学领域的一个主要焦点是寻找具有大自旋霍尔效应的材料，其特征是自旋霍尔角。这导致了对广泛材料中自旋霍尔角的定量测定，包括首席研究员S小组对3d和5d过渡金属的系统测量。事实上，由于d电子的大轨道矩，过渡金属表现出一些最大的自旋霍尔角，这表明由于理论预测的巨大的f轨道矩和大的原子序数，过渡金属有可能在稀土金属中发现更大的自旋霍尔效应。然而，稀土金属中的自旋霍尔效应到目前为止基本上还没有被研究过。铁磁共振自旋泵浦YIG薄膜中的纯自旋电流到金属中是表征逆自旋霍尔效应和提取自旋霍尔角的一种通用和可靠的技术。该项目有以下目标：(1)了解纯镧系稀土金属的本征自旋霍尔效应，揭示4f电子在自旋霍尔效应中的作用；(2)研究铜和金中稀土杂质引起的外在自旋霍尔效应；(3)表征稀土金属和其他材料之间的界面自旋电导，以了解界面上的自旋转移效率。这项研究的预期结果是系统和定量地了解稀土金属中的自旋霍尔物理，原则上，它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.