Spin-to-charge current conversion in systems with spin-orbit coupling

Abstract

This thesis is based on the experimental study of spin-to-charge current conversion (SCC) phenomena that occur in systems with spin-orbit coupling: spin Hall effect (SHE) and anomalous Hall effect (AHE). The main objective is to unveil the mechanisms that give rise to SCCs, in order to show the path to enhance the conversion efficiency for plausible technological applications. In the first part, the SHE is studied in Pt and Ta using the spin absorption technique. The weight of intrinsic and extrinsic mechanisms is extracted and a clear path to enhance the conversion efficiency is shown. Next, a Pt/graphene-based spin-to-charge current converter is explored where two orders of magnitude larger output signals, originated from SCC, have been obtained. In the second part, the relation between SHE and AHE is studied in 3d ferromagnets (FMs). The results show that both effects are not related by the current spin polarization of the FM, as it is generally assumed, and lead us to suggest the presence of an extra mechanism only in the SHE of 3d FMs. Finally, we analyse an interfacial mechanism that contributes to the AHE of Co when a Bi2O3 capping layer is added on top of the FM.