Octupole-driven spin-transfer torque switching of all-antiferromagnetic tunnel junctions

Tunneling magnetoresistance (TMR) effect and spin-transfer torque (STT) were long assumed to be negligible in tunnel junctions based on antiferromagnetic materials, since they exhibit no net magnetization. Recently, however, it was shown that all-antiferromagnetic tunnel junctions (AFMTJs) based on chiral antiferromagnets do exhibit TMR due to their non-relativistic momentum-dependent spin polarization and cluster magnetic octupole moment [1]. However, the reciprocal effect, i.e., the antiferromagnetic counterpart of STT driven by currents through the AFMTJ, has been assumed nonexistent due to the total electric current being spin-neutral. Here, we report nanoscale AFMTJs exhibiting this reciprocal effect, which we term octupole-driven spin-transfer torque (OTT) [2]. We demonstrate current-induced OTT switching of PtMn₃|MgO|PtMn₃ AFMTJs, fabricated on a thermally oxidized silicon substrate, exhibiting a record-high TMR value of 363% at room temperature and switching current densities of the order of 10 MA/cm². Our theoretical modeling explains the origin of OTT in terms of the imbalance between intra- and inter-sublattice spin currents across the AFMTJ, and equivalently, in terms of the non-zero net cluster octupole polarization of each PtMn₃ layer. This work provides a pathway towards deeply scaled magnetic memory and room-temperature terahertz technologies.

[1] Adv. Mater. 36, 2312008 (2024)

[2] arXiv:2509.03026