Charge-to-Spin Conversion Efficiency in Synthetic Antiferromagnetic System Using Pt–Cu/Ir/Pt–Cu Spacer Layers

Damping-like spin–orbit torque (SOT) efficiency (effective spin Hall angle:
$\xi _{\mathrm {DL}}$
) is investigated in synthetic antiferromagnetic (AF) systems using Pt–Cu alloy/Ir/Pt–Cu alloy spacer layers. We found AF interlayer exchange coupling through Pt–Cu alloy/Ir/Pt–Cu alloy spacer layers. We also found that the magnitude of
$\xi _{\mathrm {DL}}$
for synthetic AF system using Pt57Cu43 alloy/Ir/Pt57Cu43 alloy spacer layer is larger than that for synthetic AF system using Pt/Ir/Pt spacer layer with the same magnitude of interlayer exchange coupling (
$J_{\mathrm {ex}}$
), compared to devices with nearly similar magnitudes of
$J_{\mathrm {ex}}$
of 0.11 mJ/m2. The observed maximum magnitude of
$\xi _{\mathrm {DL}}$
is 19.9% for the synthetic AF system with Pt57Cu43 alloy/Ir/Pt57Cu43 alloy spacer layer. The use of the spacer layers with a material having a large damping-like SOT efficiency and strong interlayer exchange coupling is important for increasing spin Hall angle in synthetic AF systems.