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

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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.