Enhancement of interfacial spin transparency in Py/NiO/Pt heterostructure

This work reports the enhancement of damping-like and field-like spin-orbit torque (SOT) efficiencies and interfacial spin transparency (T-in) in the Py/NiO/Pt heterostructure. The SOT efficiencies and T-in are characterized by combining the spin-torque ferromagnetic resonance (ST-FMR) and the spin-pumping (SP) techniques. The inevitable inverse spin Hall voltage contamination induced by SP in the ST-FMR spectrum is extracted and subtracted by combining additional SP measurements, which allows obtaining accurate SOT efficiencies and T-in. The damping-like and field-like SOT efficiencies vary with the NiO insertion layer thickness, which is a result of the change of T-in. The maximum T-in reaches similar to 0.82 for a 0.6 nm-thick NiO layer. This work shows that NiO insertion is an effective method for enhancing T-in and, hence, the SOT efficiency.