Quantitative analysis of vectorial torques in a thin <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>Co</mml:mi></mml:math> 3<i>d</i> ferromagnet using orbital-spin conversion

Recent studies in orbitronics have found large current-induced torques originating---in the current understanding---from incident orbital currents. These can be generated by the orbital Rashba-Edelstein effect (OREE) produced at the interface between some light metals and their oxide films, e.g., by a naturally oxidized copper layer (${\mathrm{Cu}}^{\ensuremath{\ast}}$). In the present work, using second-harmonic Hall techniques, we determine the ratio of orbital vs spin currents exerting torques on thin transition-metal $\mathrm{Co}$ ferromagnets in systems using an orbit-to-spin $\mathrm{Pt}$ converter as an interlayer with ${\mathrm{Cu}}^{\ensuremath{\ast}}$. Our results quantifying damping-like torques show that both orbital and spin contributions are enhanced in these systems. Moreover, the experimental determination of the decoherence length in a sample series with varying $\mathrm{Co}$ thickness clearly demonstrates the interfacial generation of the orbital currents in ${\mathrm{Cu}}^{\ensuremath{\ast}}$ by the OREE, leading to subsequent magnetic torque in $\mathrm{Co}$ over a typical length scale of several nanometers.