Spin-torque-driven gigahertz magnetization dynamics in the non-collinear antiferromagnet MnSn.

Non-collinear antiferromagnets, such as MnSn, stand out for their topological properties and potential in antiferromagnetic spintronics. This emerging field aims at harnessing ultrafast magnetization dynamics of antiferromagnets through spin torques. Here we report the time-resolved dynamics of MnSn on a picosecond timescale, driven by an optically induced spin current pulse. Our results reveal that the magnetization of MnSn tilts immediately after the spin current pulse and subsequently undergoes 70 GHz precession. This immediate tilting underscores the predominant role of damping-like torque stemming from spin current absorption by MnSn. We also determine the spin coherence length of MnSn to be approximately 15 nm. This value substantially exceeds that of ferromagnets, highlighting a distinct spin-dephasing process in non-collinear antiferromagnets. Our results hold promise for ultrafast applications of non-collinear antiferromagnets and enrich our understanding of their spin-transfer physics.