Study of the dynamic properties of magnetic skyrmions using diffractive ferromagnetic resonance

在手性晶格磁体和工程异质结构中，已经发现了磁性Skyrmions，即以量子化的拓扑不变量为特征的涡旋状自旋织构。它们在外场下的动力学特性对基础科学和自旋电子器件的技术应用都具有重要意义。本项目的目的是利用铁磁共振(FMR)和共振弹性软X射线散射(REXS)研究长程有序磁系统及其动力学性质。一个例子是手征晶格磁体Cu2OSeO_3中的Skyrmion晶格的三个不同的动力学模式。除了是一个良好的模型系统，这种绝缘的Skyrmion材料还具有多铁性，导致自旋感应铁电性，具有潜在的应用前景，例如微波二极管。该项目的重点是详细了解Skyrmion系统的磁化动力学，这为Skyrmion在快速开关设备中的实际应用铺平了道路。一个单独的天米子涡旋的直径约为60纳米。如此小的长度尺度需要很高的空间分辨率，因此大多数的磁显微技术都不适用。REX谱可以用光子能量调谐到铜L边的偏振软X射线来表征磁有序。由于入射X射线的偏振性质，REX对磁化矢量的三个分量具有不同的敏感性。REX对于Skyrmions的研究具有独特的优势：它对元素具有选择性，对磁序具有非常高的灵敏度，提供了可变的采样面积，并允许快速有效地获取数据。另一方面，FMR是研究动态磁特性的有力工具，如共振模式、阻尼特性以及各向异性。这些互补技术将被应用于研究各种自旋结构的自旋动力学。该项目是与钻石光源，特别是与格利特·范德兰教授小组的共同努力。通过我们的EPSRC Skyrmion赠款，我们与西部数据、日立、IBM、三星和希捷技术公司建立了工业联系。该项目与EPSRC的研究领域“凝聚态物质：磁性和磁性材料”和“自旋电子学”保持一致。

Magnetic skyrmions, i.e., vortex-like swirling spin textures characterized by a quantized topological invariant, have been found in chiral-lattice magnets and engineered heterostructures. Their dynamics under external fields is an issue of vital importance for both fundamental science, owing to their emergent quantum properties, and technological applications in spintronic devices owing to their topological protection.The aim of the Project is to use ferromagnetic resonance (FMR) and resonant elastic soft x-ray scattering (REXS) to study long-range ordered magnetic systems and their dynamic properties. One example are the three different dynamical modes of the skyrmion lattice in the chiral-lattice magnet Cu2OSeO3. Apart from being a well-characterised model system, this insulating skyrmion material has also multiferroic properties leading to spin-induced ferroelectricity with an application potential as, e.g., microwave diodes. The Project is focused on gaining understanding of the magnetisation dynamics of skyrmion systems in great detail, which paves the way for the practical use of skyrmions in fast-switching devices. An individual skyrmion vortex has the diameter of around 60 nm. Such a small length scale requires high spatial resolution, therefore most of the magnetic microscopy techniques are unsuitable. REXS can be used to characterise the magnetic ordering by using polarized soft x-rays with the photon energy tuned to the Cu L edge. Due to the polarized nature of the incidence x-rays, REXS has different sensitivities to the three components of the magnetization vector. REXS has unique advantages for the study of skyrmions: it is element-selective, has a very high sensitivity for magnetic order, provides a variable sampling area, and allows for fast and efficient data acquisition. FMR, on the other hand, is a powerful tool for the study of dynamic magnetic properties such as the resonance modes and damping characteristics, as well as anisotropies. These complementary techniques will be applied to study the spin dynamics of various spin structures. This project is a joint effort with the Diamond Light Source, and in particular with the group of Prof Gerrit van der Laan. Industrial contacts exist via our EPSRC skyrmion grant with Western Digital, Hitachi, IBM, Samsung, and Seagate Technology.This project aligns with EPSRC's research areas "Condensed Matter: Magnetism and Magnetic Materials" and "Spintronics".