Crossover between intrinsic and temperature-assisted regimes in spin-orbit torque switching of antiferromagnetic order

Intensive studies have been made on antiferromagnets as candidate materials for next-generation memory bits due to their ultrafast dynamics reaching picosecond time scales. Recent demonstrations of electrical bidirectional switching of antiferromagnetic states have attracted significant attention. However, in the presence of significant Joule heating that destabilizes the magnetic order, the timescales associated with the switching can be limited to nanoseconds or longer. Here, we present the observation of a crossover in the switching behavior of the chiral antiferromagnet Mn3Sn by tuning the magnetic layer thickness. While Joule heating interferes with switching in thicker devices, we find clear signatures of an intrinsic spin-orbit torque mechanism as the thickness is reduced, avoiding the heating effect. The suppression of heating enables switching without significant attenuation of the readout signal using pulses shorter than those required by temperature-assisted mechanisms. The crossover into the spin-orbit torque switching behavior clarifies the potential for achieving ultrafast switching as expected from the picosecond spin dynamics of antiferromagnets. Our results lay the groundwork for designing antiferromagnetic memory devices that can operate at ultrafast timescales. Recently bidirectional switching has been demonstrated for antiferromagnets, however, the characteristic time for this switching is quite long, limiting the usefulness for applications. Here, Matsuo, Higo, and coauthors demonstrate the existence of a non-thermal spin-orbit torque mechanism of switching antiferromagnetic order in Mn3Sn, allowing for switching on much shorter timescales.