Using a heavy-metal (HM) alloy layer in spin−orbit torque (SOT)based devices is an effective method for obtaining a high current−spin conversion efficiency θ SH . In this work, SOT-based spintronic devices with a Pt 100−x Ru x -alloyed HM layer are studied by applying harmonic Hall measurements and magneto-optical Kerr effect microscopy to detect the θ SH and to observe the process of current-induced magnetization switching. Both the highest θ SH of 0.132 and the lowest critical current density (J c ) of 8 × 10 5 A/cm 2 are realized in a device with x = 20, which satisfies the high SOT efficiency and low energy consumption simultaneously. The interfacial Dzyaloshinskii−Moriya interaction can be overcome by increasing the in-plane assist field. Meanwhile, the minimum in-plane field required for current-induced complete switching can be reduced to ±60 Oe. Our study reveals that using the Pt−Ru alloyed HM layer is an effective route for SOT application with enhanced performance.

The Pt 80 Ru 20 alloy has been testified to be a satisfying heavy metal layer (HM) in spin−orbit torque (SOT)-induced spintronic devices with a relatively highspin Hall angle (θ DL ) and a low critical current density. In this work, the Pt 80 Ru 20 −Co− Ni (x Ni nm)−Ru multilayers are first prepared to find the field-free SOT-induced switching by the direct coupling of out-of-plane and in-plane ferromagnetic (FM) layers. A low in-plane assist field of −20 Oe and some optimized SOT performances are observed in the devices with x Ni = 0.4 and 0.8 nm, respectively. To further enhance the performances of the devices, a 0.6 nm thin Pt 80 Ru 20 layer is inserted between two FM layers. In the Pt 80 Ru 20 −Co−Pt 80 Ru 20 −Ni (t Ni nm)−Ru multilayers, the energy consumption decreases dramatically and a higher θ DL of 0.156 is obtained in the device with t Ni = 0.8 nm. More importantly, the field-free current-induced magnetization switching is realized in the device with t Ni = 1.4 nm. Furthermore, the interfacial Dzyaloshinskii−Moyria Interaction (DMI) can be weakened by the thin insertion as well. Our results reveal that the PtRu-based spintronic devices with enhanced SOT performances and field-free SOTdriven switching can be a promising candidate in the application of SOT-induced spintronic devices.