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

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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".