磁学实验室学术报告(2017-2)

来源:   发布时间:2017-12-18


Characterisation of the Surface Skyrmions in Chiral Magnets by 
Resonant Elastic Soft X-Ray Scattering 
 
时间:2017年12月19日 14:00 
地点:中科院物理所M253 
报告人:张石磊 博士 
             Department of Physics, University of Oxford
 
 
摘要
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.
 
 
简介:
2011年毕业于北京科技大学,2016年获英国牛津大学理学博士学位。
2016-今   英国牛津大学物理系,博士后
 
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。
           
 
研究领域
Neutron and x-ray scattering, magnetic spectroscopy
 
 
邀请人:王文洪 研究员 (82649247)