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(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(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(ex)), compared to devices with nearly similar magnitudes of J(ex) of 0.11 mJ/m(2). The observed maximum magnitude of xi(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.