“…Spin–orbit torque (SOT)-based devices and related researches have become an important field since their discovery in 2011. , Unlike spin-transfer torque (STT) devices, they provide a new approach for switching the magnetization of the ferromagnetic metal (FM) layer via an in-plane current injection. − When an in-plane electric current flows through the heavy-metal (HM) layer with a strong spin–orbit coupling (SOC), like Pt, Ta, W, and Hf, − the spin current generated by the spin Hall effect (SHE) or the Rashba effect will switch the magnetization of the adjacent FM layer. ,− Typically, SOT-based devices exhibit lower energy consumption and higher efficiency, thus, they have also drawn great research attention through magnetic storage and other microdevices, such as racetrack domain wall memory, three-terminal magnetic tunnel junction, and magnetic random-access memory. − SOT-based research studies have various aspects. For instance, field-free switching has provided a promising method to design high-efficiency spintronic devices. ,− The investigations on the field-free SOT-induced magnetization switching have made great contributions to the applications of SOT-based devices. ,,, On the other hand, the enhancement of SOT efficiency (θ SH ) is also an essential point to be focused on. To increase the SOT efficiency, various methods have been applied, such as using HM layers with opposite sign of spin Hall angle on both sides of FM layers, rare-earth metal layers, and topological materials and modulating their spin transparency and spin current absorption. ,,− In addition, the methods mentioned above, alloying an HM layer is also an effective method to enhance the θ SH while keeping a relatively low resistance for SOT devices.…”