Spin-torque-driven gigahertz magnetization dynamics in the non-collinear antiferromagnet Mn₃Sn

Non-collinear antiferromagnets, such as Mn₃Sn, 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 Mn₃Sn on a picosecond timescale, driven by an optically induced spin current pulse. Our results reveal that the magnetization of Mn₃Sn 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 Mn₃Sn. We also determine the spin coherence length of Mn₃Sn 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.