Spin-orbit torques and Dzyaloshinskii-Moriya interaction in PtMn/[Co/Ni] heterostructures

Abstract

Antiferromagnet (AFM)/ferromagnet (FM) heterostructures with broken inversion symmetry are perceived to open new opportunities for nonvolatile spintronic devices. Previous studies of such systems have demonstrated an emergence of spin-orbit torques (SOTs) in the heterostructures which are strong enough to bring about magnetization reversal. The impact of broken inversion symmetry and spin-orbit coupling also leads to an emergence of the Dzyaloshinskii-Moriya interaction (DMI) which governs the magnetic configuration and magnetization reversal. In this work, we study the SOT-induced effective fields and DMI in a heterostructure with an antiferromagnetic PtMn layer and a ferromagnetic [Co/Ni] multilayer and compare the results with a reference Pt/[Co/Ni] system. Magnetotransport measurements reveal the same sign and similar magnitude of SOT-induced effective fields for the two systems while current-induced domain wall motion measurements under in-plane fields reveal the opposite sign and smaller magnitude of DMI at the PtMn/[Co/Ni] interface compared to the Pt/[Co/Ni]. The obtained results offer in-depth information concerning the manifestations of spin-orbit interactions in AFM/FM systems, which is key to understanding of static magnetic configuration and magnetization reversal for their possible applications in antiferromagnetic spintronics.