Spin-orbit torques in asymmetric Pt/Co/Pt structures

Abstract

We have studied the generation of spin-orbit torques in Pt/Co/Pt trilayers fabricated on ${\mathrm{Gd}}_{3}{\mathrm{Ga}}_{5}{\mathrm{O}}_{12}$ (GGG) and commonly used ${\mathrm{SiO}}_{2}$ substrates. By fabricating Pt/Co/Pt trilayers with symmetric thicknesses of the top and bottom Pt layers, it has been confirmed that complete cancellation of both fieldlike and dampinglike torques can be obtained on the GGG substrate. However, the spin-orbit torques cannot be completely canceled out on the ${\mathrm{SiO}}_{2}$ substrate, which suggests that a GGG substrate is more suitable for precise measurements of the spin-orbit torques. We have also fabricated asymmetric Pt/Co/Pt trilayers on a GGG substrate to generate nonzero spin-orbit torques, and a relatively strong dampinglike torque has been measured accompanied with a fieldlike torque which is about four times smaller. Furthermore, by conducting the vector measurements of the spin-orbit torques from 300 to 10 K, it has been found that the dampinglike torque only slightly varies with temperatures.