Field-free full switching of chiral antiferromagnetic order

Chiral antiferromagnets^1,2 host octupole order^3,4 and combine the advantages of antiferromagnets and ferromagnets. Despite the development of numerous switching strategies^5,6,7,8,9, the field-free full switching remains unknown, posing an important obstacle to their practical application in memory technology. Here we prepared a homo-junction constituted of Mn₃Sn(0001) bottom layer and polycrystalline Mn₃Sn top layer. The tilted Kagomé geometry in polycrystalline Mn₃Sn divides the out-of-plane spin polarization from Mn₃Sn(0001) layer^10,11 into the out-of-Kagomé-plane and in-Kagomé-plane components, generating the symmetric (antiferromagnet-type) and asymmetric (ferromagnet-type) driving forces, respectively. The former accelerates octupole rotation, whereas the latter determines switching chirality. Field-free full switching is realized in the unconventional protocol that integrates the advantages of both antiferromagnetic and ferromagnetic switching. It goes beyond the conventional full-switching framework requiring perpendicular uniaxial anisotropy^7,12. An unprecedented switching efficiency is achieved, with both current density and power consumption an order of magnitude lower than in previous configurations, by virtue of the highly efficient driving forces due to spin-torque characteristics of octupole order and the ultralow energy barrier arising from easy-plane anisotropy, overcoming their trade-off in conventional protocols. The zero-field switching also shows the advantages of octupole-programmable chirality and robustness to external magnetic field.