Modulation of spin–orbit torque by insertion of a NiO layer in a Pt/Co structure formed on Al₂O₃ and Si/SiO _x substrate

Abstract In this study, we investigated the modulation of the spin–orbit torque (SOT) caused by inserting the NiO layer at the Pt/Co interface. A similar Pt/NiO/Co structure was deposited on two different substrates, Al2O3 and Si/SiO x substrates. We found that the damping-like torque of the Al2O3 type sample is almost independent of NiO thickness (t NiO) when t NiO < 2 nm, while that of Si/SiO x type monotonically decreased with increasing t NiO. The X-ray diffraction measurement revealed that the degree of interface roughness varies between these types. This suggests that the effect of the NiO insertion on the SOT is associated with the interface roughness.