Tuning of spin-orbit torque efficiency by the interface modification in perpendicularly magnetized Pt-Co heterojunction

Spin-orbit torque (SOT) represents a critical research direction in modern magnetic memory devices. However, the damping-like SOT efficiency generated via the spin Hall effect in conventional heavy metal/ferromagnetic metal heterostructures remains relatively low. Here, we demonstrate an in-situ Ar plasma treatment method for modifying the heavy metal interface in Pt/Co heterostructures. This approach enhances the SOT efficiency without significantly altering the saturation magnetization, coercivity, or resistivity of the magnetic layer. By systematically optimizing the Ar plasma treatment duration, we achieved a peak 60% enhancement in SOT efficiency (at tp = 10 s) compared to untreated samples, coinciding with the maximum anisotropy field of the heterostructure. Furthermore, the critical current density for current-driven magnetization switching was significantly reduced in plasma-treated samples, while the switching ratio remained unaffected. This study establishes Ar plasma treatment as a universal and non-destructive technique for effectively modulating SOT efficiency and reducing switching current density in heavy metal/ferromagnetic heterostructures, providing a viable pathway for developing low-power spintronic devices.