Detection of long-range orbital-Hall torques

We report and quantify a large orbital-Hall torque generated by Nb and Ru, which we identify from the strong dependence of torques on the ferromagnets. This is manifested as strong enhancement in the dampinglike torques measured in Nb (or Ru)/Ni bilayers as compared to Nb (or Ru)/FeCoB bilayers including the sign reversal in the case of Nb/(Ni or FeCoB) samples. We experimentally observe a striking enhancement of the measured torques with the increase of ferromagnetic Ni thickness which is markedly different from the regular spin-transfer torque; this could be a unique signature of long-range action of the orbital-Hall torques.

Automated summary

We report and quantify a large orbital-Hall torque generated by Nb and Ru in this study, identified by the strong dependence of the torques on the ferromagnets. We observed a strong enhancement in the dampinglike torques measured in Nb (or Ru)/Ni bilayers compared to Nb (or Ru)/FeCoB bilayers, including a sign reversal in the case of Nb/(Ni or FeCoB) samples. Furthermore, we discovered a significant increase in the measured torques with the increase of ferromagnetic Ni thickness, which may indicate the unique signature of long-range action of the orbital-Hall torques.