Spin pumping and large field-like torque at room temperature in sputtered amorphous WTe2-x films

We studied the spin-to-charge and charge-to-spin conversion at room temperature in sputtered WTe2-x (x = 0.8) (t)/Co20Fe60B20(6 nm) heterostructures. Spin pumping measurements were used to characterize the spin-to-charge efficiency, and the spin efficiency was calculated to be larger than similar to 0.035. Second harmonic Hall measurements were carried out to estimate the charge-to-spin conversion ratio. We found that the system exhibits a large field-like torque (spin torque efficiency similar to 0.1) and small damping-like torque (spin torque efficiency similar to 0.001) compared to those reported for heavy metals. High-resolution transmission electron microscopy images show that the WTe2-x layer is amorphous, which may enhance the spin swapping effect by inducing large interfacial spin-orbit scattering, thus contributing to a large field-like torque.