Tuning the spin-orbit torque effective fields by varying Pt insertion layer thickness in perpendicularly magnetized Pt/Co/Pt(t)/Ta structures

We experimentally determine that a Pt layer insertion between the Co/Ta interface can effectively negate the field-like spin-orbit torque (SOT) in perpendicularly magnetized Pt/Co/Pt(t)/Ta structures, as the Rashba effects at the Pt/Co and Co/Pt interfaces counteract each other. The damping-like term can be tuned by varying the thickness of the Pt insertion layer to change both the sign and magnitude of the SOT effective fields. An asymmetric SOT contribution from the Pt/Co and Co/Pt interfaces was found, leading to zero damping-like SOT being obtained at different inserted Pt and bottom Pt layer thickness. The ability to change the sign of damping-like SOT allows control over the magnetic switching direction in SOT devices.