Asymmetric spin torque：a new picture for Néel vector control in antiferromagnets

Antiferromagnets are promising candidates for next-generation spintronic devices because of their zero net magnetization, vanishing stray fields, and terahertz-scale dynamics. Deterministic control of the Néel vector by spin torque is crucial for electrical writing in antiferromagnetic devices. For collinear antiferromagnets, however, the conventional spin torque picture based on two idealized limits of spin accumulation—perfectly uniform or strictly staggered—does not adequately describe the writing process in realistic device structures. In practice, interface effects, sublattice stacking, and symmetry breaking often make spin accumulation on the two sublattices unequal, giving rise to an asymmetric spin torque. This mechanism reveals how angular momentum transfer occurs in realistic antiferromagnetic devices through locally inequivalent sublattice responses, thereby determining the dynamical trajectory and final state of the Néel vector. Asymmetric spin torque thus provides a new physical picture for Néel vector control and a useful framework for understanding and achieving efficient, deterministic writing in realistic antiferromagnetic devices.