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The manipulation of antiferromagnetic order by means of spin-orbit torques opens unprecedented opportunities to exploit the dynamics of antiferromagnets in spintronic devices. In this work, we investigate the current-induced switching of the magnetic octupole vector in the Weyl antiferromagnet Mn$_3$Sn as a function of pulse shape, field, temperature, and time. We find that the switching behavior can be either bistable or tristable depending on the temporal structure of the current pulses. Time-resolved Hall effect measurements reveal that Mn$_3$Sn switching proceeds via a two-step demagnetization-remagnetization process caused by self-heating over a timescale of tens of ns followed by cooling in the presence of spin-orbit torques. Our results shed light on the switching dynamics of Mn$_3$Sn and prove the existence of extrinsic limits on its switching speed., Rectified wrong order of MS and Supplement

We report the observation of a unidirectional magnetoresistance (UMR) that originates from the nonequilib-rium orbital momentum induced by an electric current in a naturally oxidized Cu/Co bilayer. The orbital UMR scales with the torque efficiency due to the orbital Rashba-Edelstein effect upon changing the Co thickness and temperature, reflecting their common origin. We attribute the UMR to orbital-dependent electron scattering and orbital to spin conversion in the ferromagnetic layer. In contrast to the spin current induced UMR, the magnon contribution to the orbital UMR is absent in thin Co layers, which we ascribe to the lack of coupling between low-energy magnons and orbital current. The magnon contribution to the UMR emerges in Co layers thicker than about 5 nm, which is comparable to the orbital to spin conversion length. Our results provide insight into orbital-to spin-momentum transfer processes relevant for the optimization of spintronic devices based on light metals and orbital transport., Physical Review Research, 4 (3), ISSN:2643-1564