Unveiling the mechanisms of the spin Hall effect in Ta

TL;DR

This paper experimentally demonstrates that the intrinsic mechanism dominates the spin Hall effect in highly-resistive tantalum, enabling a significant enhancement of the spin Hall angle and advancing spintronic device efficiency.

Contribution

It provides the first direct experimental evidence that the intrinsic mechanism is dominant in Ta and shows how tuning resistivity enhances the spin Hall angle.

Findings

Intrinsic spin Hall conductivity in β-Ta is -820±120 (ħ/e) Ω^{-1}cm^{-1}.

The spin Hall angle in Ta can be linearly increased up to -35±3%.

Intrinsic mechanism dominance enables large spin Hall angles in pure metals.

Abstract

Spin-to-charge current interconversions are widely exploited for the generation and detection of pure spin currents and are key ingredients for future spintronic devices including spin-orbit torques and spin-orbit logic circuits. In case of the spin Hall effect, different mechanisms contribute to the phenomenon and determining the leading contribution is peremptory for achieving the largest conversion efficiencies. Here, we experimentally demonstrate the dominance of the intrinsic mechanism of the spin Hall effect in highly-resistive Ta. We obtain an intrinsic spin Hall conductivity for $\beta$-Ta of -820$\pm$120 ($\hbar$/e) $\Omega^{-1}cm^{-1}$ from spin absorption experiments in a large set of lateral spin valve devices. The predominance of the intrinsic mechanism in Ta allows us to linearly enhance the spin Hall angle by tuning the resistivity of Ta, reaching up to -35$\pm$3%, the largest reported value for a pure metal.