Spin-Orbit Torques in NbSe2/Permalloy Bilayers

We present measurements of current-induced spin-orbit torques generated by NbSe2, a fully metallic transition-metal dichalcogenide material, made using the spin-torque ferromagnetic resonance (ST-FMR) technique with NbSe2/Permalloy bilayers. In addition to the out-of-plane Oersted torque expected from current flow in the metallic NbSe2 layer, we also observe an in-plane antidamping torque with torque conductivity sigma(S) approximate to 10(3) (h/2e)(Omega m)(-1) and indications of a weak field-like contribution to the out-of-plane torque oriented opposite to the Oersted torque. Furthermore, in some samples we also measure an in-plane field-like torque with the form (m) over cap x (z) over cap, where (m) over cap is the Permalloy magnetization direction and (z) over cap is perpendicular to the sample plane. The size of this component varies strongly between samples and is not correlated with the NbSe2 thickness. A torque of this form is not allowed by the bulk symmetries of NbSe2 but is consistent with symmetry breaking by a uniaxial strain that might result during device fabrication.