Ultrafast magnetization dynamics in the magnetic Weyl semimetal Co₃Sn₂S₂

Co₃Sn₂S₂ is a new magnetic Weyl semimetal, in which strong intrinsic anomalous Hall effect and optical nonlinear responses are found. It has attracted significant interest in exploring its topological and magnetic properties. In this talk, we report on ultrafast magnetic dynamics in this material using time-resolved magneto-optics Kerr rotation. We find both coherent magnon oscillations and thermally driven ultrafast demagnetization. The ferromagnetic resonance (FMR) frequency is measured to be hundreds of gigahertz at low temperatures, which is much faster than other traditional FMR frequencies. The demagnetization dynamics depend strongly on the temperature, showing critical slowing down near the Curie temperature. We also extract the anisotropy field value, magnon lifetime and demagnetization time from the measurements. Our experiment sheds new light on the magnetization dynamics in this novel magnetic Weyl semimetal.