Quantitative analysis of vectorial torques in a thin Co3d 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 (Cu - ). In the present work, using second-harmonic Hall techniques, we determine the ratio of orbital vs spin currents exerting torques on thin transition-metal Co ferromagnets in systems using an orbit-to-spin Pt converter as an interlayer with Cu - . 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 Co thickness clearly demonstrates the interfacial generation of the orbital currents in Cu - by the OREE, leading to subsequent magnetic torque in Co over a typical length scale of several nanometers.