Spin–torque generator engineered by natural oxidation of Cu

TLDR

The spin Hall effect, a spin–orbit coupling phenomenon, enables electric generation and detection of spin currents and underpins spintronic devices, yet heavy metals have traditionally been considered essential for efficient spin‑torque generation. By naturally oxidizing copper, the authors dramatically enhanced its spin Hall effect, boosting spin‑torque efficiency in a Cu/NiFe bilayer by over two orders of magnitude to match Pt‑based systems and demonstrating that oxygen control can replace heavy metals in spin‑torque generators.

Abstract

Abstract The spin Hall effect is a spin–orbit coupling phenomenon, which enables electric generation and detection of spin currents. This relativistic effect provides a way for realizing efficient spintronic devices based on electric manipulation of magnetization through spin torque. However, it has been believed that heavy metals are indispensable for the spin–torque generation. Here we show that the spin Hall effect in Cu, a light metal with weak spin–orbit coupling, is significantly enhanced through natural oxidation. We demonstrate that the spin–torque generation efficiency of a Cu/Ni 81 Fe 19 bilayer is enhanced by over two orders of magnitude by tuning the surface oxidation, reaching the efficiency of Pt/ferromagnetic metal bilayers. This finding illustrates a crucial role of oxidation in the spin Hall effect, opening a route for engineering the spin–torque generator by oxygen control and manipulating magnetization without using heavy metals.