Manipulation of spin–orbit torque and Dzyaloshinskii-Moriya interaction by varying Mn concentration in Pt_1-xMn_x/Co bilayer

Reducing critical current density (J_C) of current-driven magnetization switching via power-efficient spin–orbit torque (SOT) is a key challenge in spin-based memory and logic devices. The Pt_1-xMn_x alloy shows prospect for enhancing the damping-like SOT efficiency (ξ_DL) while maintaining relatively low resistivity and power consumption. In this work, we investigated the Mn concentration x dependence of ξ_DL in Pt_1-xMn_x/Co bilayer and observed a nonmonotonic variation with the maximum ξ_DL ≈ 0.25 appearing around x = 0.2. The increase of the Pt_1-xMn_x layer resistivity is the main contribution to the enhancement of ξ_DL. Mn atoms doped in Pt not only modulate ξ_DL originating from the spin Hall effect of the Pt_1-xMn_x layer, but also affect the interfacial phenomena at the Pt_1-xMn_x/Co interface. We find that the related interfacial Dzyaloshinskii-Moriya interaction (DMI) is also tunable by x with the maximum appearing around x = 0.15. The significantly reduced J_C of Pt_1-xMn_x/Co bilayer is mainly due to the enhancement of ξ_DL and the attenuation of effective perpendicular magnetic anisotropy energy density. Meanwhile, Pt_1-xMn_x/Co bilayer maintains low power consumption and necessary thermal stability. Our work highlights the potential of alloying Pt with Mn as a valuable means to achieve high-performance SOT spintronic devices.