Exploring orbital-charge conversion mediated by interfaces with CuOx through spin-orbital pumping

We explore the impact of different materials on orbital-charge conversion in heterostructures with a naturally oxidized copper capping layer. Introducing a thin layer of $\mathrm{Cu}{\mathrm{O}}_x$ (3 nm) to the yttrium iron garnet (YIG)/W heterostructure resulted in a notable decrease in signal when employing the spin pumping (SP) technique. This contrasts with prior findings in YIG/Pt, where the addition of $\mathrm{Cu}{\mathrm{O}}_x$ (3 nm) led to a significant signal enhancement. Conversely, the introduction of the same $\mathrm{Cu}{\mathrm{O}}_x$ (3 nm) layer to YIG/Ti (4 nm) structure showed no change in the SP signal. This lack of change is attributed to the fact that Ti, unlike Pt, does not generate an orbital current at the $\mathrm{Ti}/\mathrm{Cu}{\mathrm{O}}_x$ interface due to its weaker spin-orbit coupling. Notably, incorporating the $\mathrm{Cu}{\mathrm{O}}_x$ (3 nm) layer on top of Si/Py (5 nm)/Pt (4 nm) structures resulted in a substantial increase in the spin pumping signal. However, in $\mathrm{Si}/\mathrm{Cu}{\mathrm{O}}_x$ (3 nm)/Pt (4 nm)/Py (5 nm) structures, the signal exhibited a decrease. Finally, we applied a phenomenological model of the spin (orbital) Hall effect in YIG/heavy-metal systems to refine our data. These discoveries have the potential to advance research in the innovative field of orbitronics and contribute to the development of new technologies based on spin-orbital conversion.