Characterisation of the Surface Skyrmions in Chiral Magnets by Resonant Elastic Soft X-Ray Scattering
Department of Physics, University of Oxford
在国际SCI收录的Nature Communication, Nano Letter, Phys. Rev.B 等重要学术期刊发表论文30余篇，引用220余次。
Neutron and x-ray scattering, magnetic spectroscopy
Magnetic skyrmions are magnetisation swirls that present topological properties, leading to a number of novel physics, such as emergent electromagnetism and non-trivial magnetic dynamics. The prototypical skyrmion-hosting materials are chiral magnets, such as MnSi, FeCoSi, FeGe and Cu2OSeO3, in which the long-range ordered skyrmion lattice is found as the bulk state. Depending on the material, the individual skyrmion size in chiral magnets falls in the range of 3-100 nm. Here, I present our recent results on charactering the skyrmion structures in such length-scale, using resonant elastic x-ray scattering (REXS). Unlike neutrons or hard x-rays scattering, we utilise long wavelength, small attenuation-length soft x-ray beam as the probe. This leads to considerably large scattering cross-section for 3d and rare-earth magnetic elements, better reciprocal space resolution, as well as excellent surface sensitivity. First, I will show that the surface skyrmions behave unexpectedly different from that is found in the bulk. It presents multidomain state, and strong surface-pinning effect. Both effects are favoured by device applications. Second, I will demonstrate that REXS is able to reconstruct the very fine internal structure of an individual skyrmion, inaccessible to other magnetic characterisation techniques. This allows us to accurately measure the microscopic interactions of the material system. Lastly, I will show an in-situ REXS measurement by applying a magnetic field gradient, under which the skyrmions undergo concentric rotation with well-defined slow dynamics. This provides an effective way of controlling the skyrmions towards the racetrack memory embodiment.
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