We report the experimental demonstration of long-range orbital torques generated by Nb and Ru and detected by spin-torque ferromagnetic resonance (ST-FMR) measurements in Nb/Ni and Ru/Ni bilayers. We identify the orbital torques from the sign-reversal and a strong enhancement in the damping-like torque observed in Nb (Ru)/Ni bilayers as compared to Nb (Ru)/FeCoB bilayers as theoretically predicted1. The long-range nature of orbital transport in the ferromagnet was revealed by varying the thickness of Ni in Nb (Ru)/Ni bilayers which is markedly different compared to the regular spin absorption in the ferromagnet that takes place in the first few layers confirming the recent prediction2. Finally, we show that the external injection of orbital current in a heavy metal such as Pt can convert the orbital current into a spin-current leading to higher switching efficiency and the enhanced spin-current generation that could both be potentially attractive for the application3,4.
References 1. Go, D. & Lee, H.-W. Orbital torque: Torque generation by orbital current injection. Phys. Rev. Res. 2, 013177 (2020). 2. Go, D. et al. Long-Range Orbital Magnetoelectric Torque in Ferromagnets. arXiv 2106.07928, 1–6 (2021). 3. Ding, S. et al. Harnessing Orbital-to-Spin Conversion of Interfacial Orbital Currents for Efficient Spin-Orbit Torques. Phys. Rev. Lett. 125, 177201 (2020). 4. Go, D., Jo, D., Lee, H.-W., Kläui, M. & Mokrousov, Y. Orbitronics: Orbital currents in solids. EPL (Europhysics Lett. 135, 37001 (2021). 5.