Epitaxially grown multilayers, ${\mathrm{Mn}}_3\mathrm{PtN}/\mathrm{Cu}/{\mathrm{Co}}_{20}{\mathrm{Fe}}_{60}{\mathrm{B}}_{20}$, with a thickness of the Cu spacer layers from 0 to 5 nm, were prepared on (100)-oriented MgO substrates. The multilayer exhibited a pronounced exchange bias field in the absence of a Cu spacer, which became minimal with the introduction of a finite Cu spacer. We measured spin-torque ferromagnetic resonance to estimate the spin-Hall angle (${\theta }_{\mathrm{SH}}$) in the multilayers, emphasizing the role of the Cu spacer layer in the spin current transport across the interface. We found that both ${\theta }_{\mathrm{SH}}$ and the effective Gilbert damping parameter decrease significantly upon the insertion of Cu, suggesting that the spin-orbit torque (SOT) primarily originates from interfaces. A correlation between SOT and exchange bias with the Cu spacer layer indicates the significance of interfacial contributions. These experimental results demonstrate the critical importance of interfacial engineering in antiferromagnetic-based spintronics, revealing an alternative mechanism for generating spin torque in magnetic heterostructures that is essential for controlling magnetization dynamics in energy-efficient spintronics applications.

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• Magnetic anisotropy
• Magnetic coupling
• Magnetism
• Magnetization dynamics
• Spin dynamics
• Spintronics