Spin–orbit torque control via distinct exchange-coupling interfaces

Efficient manipulation of magneto-dynamics is critical for advancing nonvolatile spin memory devices, and high spin–orbit torque (SOT) efficiency enables rapid and energy-efficient magnetization switching. One promising strategy to enhance SOT efficiency involves interface engineering, where spin transmission is modulated through interfacial exchange coupling in magnetic heterostructures. Here, we construct two distinct types of exchange-coupling interfaces: a self-assembled antiferromagnetic coupling (AFC) interface (Py/Ho) and an intrinsic exchange-coupled AFC interface (Py/FeMn), to systematically investigate their influences on SOT efficiency. Both spin dynamic damping and SOT efficiency are significantly enhanced in Py/X (X = Ho, FeMn) compared to their Cu spacer counterparts, Py/Cu/X (X= Ho, FeMn), highlighting the key contribution of AFC interface in facilitating efficient spin transmission. Notably, the Py/Ho interface enables the generation of spin currents with out-of-plane spin polarization—an effect absent in the Py/FeMn system. Moreover, the SOT efficiency in the Py/Ho system, modulated by the self-assembled AFC interface, exhibits pronounced frequency dependence, whereas the exchange-coupled AFC in Py/FeMn leads to a nearly frequency-independent behavior. This frequency-dependent behavior is likely attributed to magnon coupling at the Py/Ho interface, where the low-energy self-assembled AFC state allows dynamic coupling with the adjacent Py layer. These findings highlight the critical role of exchange-coupling interfaces in governing spin transmission and SOT behavior, enabling the design of low-power spintronic devices.