Spin Hall effect in 5d Au: W transition metal alloys (Conference Presentation)

The spin Hall effect (SHE) [1] allows for a reciprocal conversion between charge and spin currents using the spin orbit coupling which can be at the core of several promising spintronics devices. The spin orbit interaction is used to produce a transverse flow of spin or charge in response to a longitudinal excitation, these are the direct or inverse SHE. The spin Hall angle (SHA), the ratio of longitudinal and transverse electronic conductivities, is the characterizing parameter of this conversion. So far, large SHA have been reported in transition metals like Pt, Pd, W, Beta-Ta and in a few alloys with large spin orbit coupling impurities: CuIr, CuBi or CuPb [2]. In this presentation we will report on our study of the SHA in AuW alloys [3] which exhibits a non-monotonic relation with the W concentration. In the regime of diluted alloys the behaviour suggests a dominant side-jump contribution to the spin Hall resistivity, the SHA increasing with the W concentration. We will present experiments demonstrating the requirement of new spin-absorption model in lateral spin valves adapted to the case of strong spin absorption for a correct evaluation of the SHA. Altogether with complementary Ferromagnetic Resonance Spin-Pumping studies, it then leads to SHA as large as +15%. At higher W content the SHA sign is reversed, becoming negative as for pure W.