Effect of an ultrathin rare-earth Dy interlayer on the spin-orbit torques and interfacial Dyzaloshinskii-Moriya interaction in perpendicularly magnetized Pt/Dy/Co multilayers

Abstract

Spin-source/ferromagnet interfaces in spin–orbit torque (SOT) devices play a significant role in efficient spin-current generation, transport and interfacial interactions. In this study, an ultrathin rare-earth Dy layer with a thickness of 0.6 nm was inserted into the Pt/Co interface to explore its impact on SOT-driven magnetization reversal. Anomalous Hall effect measurements reveal an increase of the damping-like SOT efficiency by ∼480 %, alongside a reduced switching current density of ∼6.68 × 10⁶ A/cm² in a perpendicularly magnetized Pt/Dy/Co/Ta stack. In particular, a notable increase of the field-like SOT efficiency by ∼1000 % and the large effective spin Hall angle of ∼0.491 reveal the enhanced interfacial Rashba spin–orbit coupling and/or spin transparency by the Dy decoration. More importantly, a field-free SOT reversal was observed, which may originate from the out-of-plane Rashba effective magnetic field owing to the lateral inhomogeneous component distribution between Dy and Co. Furthermore, an enhanced interfacial Dyzaloshinskii-Moriya interaction (DMI) was achieved in the Pt/Dy/Co/Ta stack. Our results demonstrate that interface engineering with an ultrathin rare-earth Dy interlayer can significantly strengthen the interfacial effects, such as interfacial spin–orbit coupling, spin transparency, and DMI, providing a promising approach to manufacturing energy-efficient SOT-based spin memories and racetrack devices.