Process gas dependence of spin–orbit torque in Pt/NiO/Co structures.

Recently, to enlarge spin-current-induced phenomena, such as spin–orbit torque (SOT) in a ferromagnet (FM)/heavy-metal (HM) bilayer, enhancement of spin-current transmittance by inserting an antiferromagnetic insulator at the FM/HM interface has been extensively studied. In this study, we have investigated the SOT modulation in a Pt/NiO/Co structure in which the NiO layer was deposited using Ar and Xe process gases. Consequently, the quality of the NiO layer could be regulated. An increase in the damping-like SOT efficiency was observed by inserting the 1 nm NiO layer in the Ar type while it monotonically decreased with an increase in the NiO thickness in the Xe type. Significant temperature dependence of the SOT efficiency in the Ar type indicates that thermal magnon largely contributes to the spin-current propagation. X-ray diffraction measurement result suggests that the difference in crystallinity of the NiO layer between the Ar and Xe types attributes to the different SOT modulations. [ABSTRACT FROM AUTHOR]