Reversal of noncollinear antiferromagnets with an octupole moment by chirped spin-orbit torque

Electrical manipulation of chiral noncollinear antiferromagnetic (AFM) order via spin-orbit torque (SOT) has attracted significant attention in terms of both fundamental insights and applications in information technology. Here we investigate the alternating chirped current pulse (ACCP) driven resonant excitation of noncollinear AFM order of pristine Mn₃Sn, and thus achieves efficient reversal of octupole moment, defined as a cluster magnetic order parameter, without an external field. The reversal proceeds via out-of-plane rotation of the octupole moment, whose precessional dynamics exhibit a counter-rotation relative to the atomic moments. The enhanced efficiency of field-free deterministic switching arises from resonant energy exchange between the octupole moment and the SOT fields in ACCP: the octupole moment resonantly absorbs (emits) energy from (to) the SOT fields before (after) crossing the energy barrier. Therefore, these findings deepen the understanding of field-free SOT-driven octupole moment dynamics and propose a pathway toward ultrafast, low-power spintronic devices.