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

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 Wand 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. (c) 2023 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

Automated summary

Magnetization switching can be achieved by utilizing spin-orbit torque, which shows potential for developing non-volatile memory technologies. In this study, we observed 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, with an estimated efficiency comparable to contemporary spintronic materials. We propose that the Rashba Edelstein effect and the spin-orbit proximity effect contribute to the charge-to-spin current conversion and the giant efficiency, respectively.