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

Abstract Interlayer exchange coupling (IEC) plays a critical 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 (RKKY) 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, regardless of the coupling type. 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 efficiency, 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-efficient next-generation spintronic devices.