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/Ni81Fe19 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.
Highlights
The spin Hall effect is a spin–orbit coupling phenomenon, which enables electric generation and detection of spin currents
In the presence of the spin–orbit interaction, a non-zero spin current is generated in a direction perpendicular to an applied charge current, which is known as the direct spin Hall effect (DSHE)[12,13,14,15,16,17,18,19]
Our experimental finding is that the spin–torque generation efficiency of the Cu/Ni81Fe19 bilayer is significantly enhanced by the natural oxidation; the spin–torque generation efficiency of the naturally oxidized Cu/Ni81Fe19 bilayer is comparable to that of Pt/ferromagnetic metal bilayers
Summary
The spin Hall effect is a spin–orbit coupling phenomenon, which enables electric generation and detection of spin currents. We demonstrate that the spin–torque generation efficiency of a Cu/Ni81Fe19 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. To realize efficient spin-charge conversion, it has been believed that heavy metals with strong spin–orbit interaction are indispensable This largely limits the selection of materials for the practical application of the spin Hall devices. These results provide a way for engineering the spin–torque generator driven by the DSHE through oxidation control
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