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 NiO layer at Pt/Co interface. The similar Pt/NiO/Co structure was deposited on two different substrates, Al2O3 and Si/SiOx substrates. We found that the damping-like torque of the Al2O3 type sample is almost independent of NiO thickness (tNiO) when tNiO < 2 nm, while that of Si/SiOx type monotonically decreased with increasing tNiO. 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.