Observation of charge-to-spin conversion with giant efficiency at Ni0.8Fe0.2/Bi2WO6 interface

Abstract

Magnetization switching using spin–orbit torque offers a promising route to developing non-volatile memory technologies. The prerequisite, however, is the charge-to-spin current conversion, which has been achieved traditionally by harnessing the spin–orbit interaction in heavy metals, topological insulators, and heterointerfaces hosting a high-mobility two-dimensional electron gas. Here, we report the observation of charge-to-spin current conversion at the interface between ferromagnetic Ni0.8Fe0.2 and ferroelectric Bi2WO6 thin films. The resulting spin–orbit torque consists of damping-like and field-like components, and the estimated efficiency amounts to about 0.48 ± 0.02, which translates to 0.96 ± 0.04 nm−1 in terms of interfacial efficiency. These numbers are comparable to contemporary spintronic materials exhibiting giant spin–orbit torque efficiency. We suggest that the Rashba Edelstein effect underpins the charge-to-spin current conversion on the interface side of Ni0.8Fe0.2. Further, we provide an intuitive explanation for the giant efficiency in terms of the spin-orbit proximity effect, which is enabled by orbital hybridization between W and Ni (Fe) atoms across the interface. Our work highlights that Aurivillius compounds are a potential addition to the emerging transition metal oxide-based spin–orbit materials.