SKM 2023 – scientific programme
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MA: Fachverband Magnetismus
MA 4: Spin Transport and Orbitronics, Spin-Hall Effects (joint session MA/TT)
MA 4.7: Talk
Monday, March 27, 2023, 11:00–11:15, HSZ 403
Long-range orbital-Hall torques in Nb(or Ru)/Ni Heterostructures — Arnab Bose1, Fabian Kammerbauer1, •Rahul Gupta1, Dongwook Go2, Yuriy Mokrousov1,2, Gerhard Jakob1, and Mathias Kläui1,3 — 1Institute of Physics, Johannes Gutenberg University Mainz, Staudingerweg 7, 55128 Mainz, Germany — 2Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, 52425 Jülich, Germany — 3Center for Quantum Spintronics, Department of Physics, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway
We report a large orbital Hall torque (OHT) generated by Nb and Ru via strong dependence of torques on the ferromagnets, Ni, in Nb(Ru)/Ni heterostructures. We found the sign reversal of the damping-like torque in Nb/Ni. Moreover, the long-range orbital transport in the ferromagnet was revealed by the thickness dependences of Ni in Ni/Nb(or Ru) heterostructure, which are markedly different from the regular spin absorption in the ferromagnet that takes place within a few angstroms and thus it uniquely distinguishes OHT from the spin Hall torque. The experimentally measured effective orbital-Hall conductivities are found to be 6.1×104 ℏ/2e (Ωm)−1 and 5.86×104 ℏ/2e (Ωm)−1 for Nb and Ru, respectively, which is an order of magnitude higher than their measured spin Hall conductivities, as also confirmed by the density functional theory. This study opens a plethora of possibilities to further engineering the torques, utilizing the orbital degree of freedom.