Deterministic Switching of the N\'{e}el Vector by Asymmetric Spin Torque

TL;DR

This paper demonstrates a universal mechanism for deterministic switching of the Neel vector in antiferromagnets using asymmetric spin torque, enabling versatile, field-free control crucial for AFM spintronic devices.

Contribution

It introduces a novel switching mechanism based on asymmetric spin torque, combining analytical derivation and simulations, applicable to all collinear antiferromagnets.

Findings

Asymmetric spin torque enables Neel vector switching.

Both field-like and damping-like components contribute cooperatively.

Versatile switching strategies are demonstrated, including field-free methods.

Abstract

N\'eel vector, the order parameter of collinear antiferromagnets, serves as a state variable in associated antiferromagnetic (AFM) spintronic devices to encode information. A deterministic switching of N\'eel vector is crucial for the write-in operation, which, however, remains a challenging problem in AFM spintronics. Here we demonstrate, based on analytical derivation and macro-spin simulations, that N\'eel vector switching can be generally achieved via a current-induced spin torque, provided the spin accumulations responsible for this torque are non-identical between opposite sublattices. This condition occurs widely in AFM films, as symmetry equivalence between sublattice-dependent spin accumulations is usually absent, allowing unequal spin accumulations induced by Edelstein effect or a spin current. Unlike previously studied spin torques induced by uniform or staggered spin accumulations -- where either the field-like or damping-like component dominates exclusively -- the asymmetric spin torque features cooperative contributions from both components, leading to N\'eel vector dynamics that are fundamentally distinct from previous expectations. Crucially, the static states stabilized by the asymmetric spin torque enable versatile N\'eel vector switching strategies -- field-free spin-transfer torque switching during current application, as well as field-free or field-assisted spin-orbit torque switching after the current pulse -- demonstrating that established spin torque techniques from ferromagnetic spintronics can be directly adapted to AFM systems, a capability absent in previous theoretical frameworks. Our work establishes a general mechanism for current-induced N\'eel vector switching, which is in principle feasible for all collinear antiferromagnets, and thus paves the route to realize efficient writing in AFM spintronics.