Spin Torque Ferromagnetic Resonance Measurements in a Bulk Rashba System

Abstract

While many researchers have focused on the interfacial Rashba effect, bulk Rashba materials have received considerable interest due to their potential to enhance spin-orbit torque (SOT). By utilizing GeTe as a bulk Rashba material in the role of a spin-orbit channel, GeTe/Ni81Fe19 and GeTe/Co40Fe40B20 bilayers are fabricated, and SOTs are investigated using the spin torque ferromagnetic (FM) resonance technique. In this method, damping-like and field-like SOTs are extracted individually, excluding thermal effects. Upon analyzing the data, a remarkable field-like SOT efficiency of 0.40 is obtained from the GeTe/Ni81Fe19 system. This high efficiency is attributed to the enhancement of interfacial spin-orbit coupling through the bulk Rashba effect of the GeTe channel. Moreover, noticeable distinctions in SOTs are observed between the Co40Fe40B20 and Ni81Fe19 interfaces, underscoring the importance of selecting the appropriate FM layer for optimizing SOT efficiency. This study highlights the promising potential of bulk Rashba materials like GeTe in advancing SOT-based devices. To effectively separate the damping-like and field-like spin-orbit torques (SOTs) in a bulk Rashba channel, a ferromagnetic (FM) resonance method is employed. In this experiment, a significant field-like torque is detected. Moreover, noticeable distinctions are observed in SOTs between the Co40Fe40B20 and Ni81Fe19 interfaces, emphasizing the importance of selecting the appropriate FM layer to enhance SOT efficiency.image (c) 2023 WILEY-VCH GmbH