Enhanced Spin–Orbit Torque Performances in PtRu–Co–PtRu–Ni–Ru-Based Spintronic Devices

The Pt80Ru20 alloy has been testified to be a satisfying heavy metal layer (HM) in spin–orbit torque (SOT)-induced spintronic devices with a relatively high-spin Hall angle (θDL) and a low critical current density. In this work, the Pt80Ru20–Co–Ni (xNi 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 xNi = 0.4 and 0.8 nm, respectively. To further enhance the performances of the devices, a 0.6 nm thin Pt80Ru20 layer is inserted between two FM layers. In the Pt80Ru20–Co–Pt80Ru20–Ni (tNi nm)–Ru multilayers, the energy consumption decreases dramatically and a higher θDL of 0.156 is obtained in the device with tNi = 0.8 nm. More importantly, the field-free current-induced magnetization switching is realized in the device with tNi = 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 SOT-driven switching can be a promising candidate in the application of SOT-induced spintronic devices.