Interlayer exchange coupling effects on the spin-orbit torque in synthetic magnets

Abstract Interlayer switching coupling (IEC) plays a determining role in spin-orbit torque (SOT) switching in synthetic magnets. This work establishes a fundamental correlation between IEC and SOT dynamics within Co/Pt-based synthetic antiferromagnets and synthetic ferromagnets. The antiferromagnetic and ferromagnetic coupling states are precisely engineered through Ruderman-Kittel-Kasuya-Yosida interactions by modulating the Ir spacer thickness. Experimental results reveal that the critical switching current density exhibits a strong positive correlation with the IEC strength, independent of the coupling nature. A comprehensive theoretical framework based on the Landau-Lifshitz-Gilbert equation elucidates how IEC contributes to the effective energy barrier that must be overcome during SOT-induced magnetization switching. Significantly, the antiferromagnetically coupled samples demonstrate enhanced SOT effciency, with the spin Hall angle being directly proportional to the antiferromagnetic exchange coupling field. These insights establish a coherent physical paradigm for understanding IEC-dependent SOT dynamics and provide strategic design principles for the development of energy-effcient next-generation spintronic devices.