Neutron and X-Ray Scattering Studies of Transition-Metal Compounds with Large Spin-Orbit Coupling

非技术摘要：含有大原子序数元素（如铱和锇）的化合物在其磁性和结构性质之间表现出强烈的相互作用，称为自旋轨道耦合。它产生了独特的和技术相关的特性，可能用于制造超导体，用于低功率电子器件的新型磁性材料和永磁体。本文提出用x射线和中子探针研究这类化合物的两种重要类型，即所谓的过渡金属二硫族化合物和六方链氧化物磁体。所获得的这些化合物的原子级晶体结构和磁性结构，以及它们的动力学性质，有望揭示这些材料中自旋轨道耦合作用的细节。由此产生的见解可能有助于未来高性能永磁体的设计，以及新型纳米级电子器件。技术摘要：电子自由度与晶格的相互作用在过渡金属化合物中产生了大量有趣的效应，如多铁性和巨磁阻。自旋轨道耦合是一种重要的磁结构耦合机制。在电子位于3d和4d壳层的系统中，SOC通常是弱的。然而，在5d材料中，它可以定性地改变材料的基本性质，从而产生新的物理效应和新的器件概念。本文提出了两类5d化合物的晶格和磁性结构及其动力学性质的x射线和中子散射研究。(1)层状过渡金属二硫族化合物。提出的研究包括研究全局和局部晶格对称性，远程和局部二聚体有序，以及它们在破坏/促进奇异超导性，磁有序和自旋极化电子带中的作用。(2)准一维六方磁体具有巨大的磁矫顽力和异常的磁各向异性。提出了场致跃迁、微观磁相互作用和磁畴的研究。目标包括了解这些化合物中不寻常的磁性，它与5d电子的物理关系，以及这种物理是否可以深入了解永磁体的功能。

Nontechnical abstract:Compounds containing elements with large atomic numbers (such as iridium and osmium) exhibit a strong interaction between their magnetic and structural properties called spin-orbit coupling. It gives rise to exotic and technologically relevant properties, potentially useful for making superconductors, novel magnetic materials for low-power electronics, and permanent magnets. Herein, studies of two important classes of such compounds, the so-called transition-metal dichalcogenides and hexagonal chain oxide magnets, using x-ray and neutron probes are proposed. The obtained atomic-level crystallographic and magnetic structures of these compounds, as well as their dynamical properties, are expected to reveal the specifics of the action of the spin-orbit coupling in these materials. The resulting insights might help in the design of future high-performance permanent magnets, as well as novel nanoscale electronic devices.Technical abstract:Interaction of electronic degrees of freedom with crystal lattice gives rise to a plethora of interesting effects in transition-metal compounds, such as multiferroicity, and colossal magnetoresistance. Spin-orbit coupling (SOC) is an important magnetostructural coupling mechanism. In systems with electrons in 3d and 4d shells, SOC is usually weak. In 5d materials, however, it can qualitatively change the basic materials properties, leading to novel physical effects and new device concepts. Herein, x-ray and neutron scattering studies of the lattice and magnetic structures, as well as their dynamical properties, are proposed for two classes of 5d compounds. (1) Layered transition-metal dichalcogenides. The proposed studies include investigations of global and local lattice symmetry, long-range and local dimer orderings, and their role in destruction/promotion of exotic superconductivity, magnetic order, and spin-polarized electronic bands. (2) Quasi-one-dimensional hexagonal magnets exhibiting colossal magnetic coercivity, and unusual magnetic anisotropies. Studies of field-induced transitions, microscopic magnetic interactions, and magnetic domains are proposed. The goals include understanding the unusual magnetism in these compounds, its relationship to the physics of 5d electrons, and whether this physics could give an insight into functioning of permanent magnets.