High-Efficiency Field-Free Spin-Orbit Switching Based on PtW Alloy Layer

Current-driven spin-orbit-torque (SOT)-induced device is a promising candidate with nonvolatility, low energy consumption, and ultrafast speed for the next-generation storage and computing technique. However, the requirement of the assistant magnetic field hinders its application. Besides, the switching current density in SOT-induced devices still needs to be further reduced. Here, we prepared devices with stacks of Ta/Pt_100-xW_x/Co/AlO_y/Pt and systematically investigated changes in the switching efficiency with W content. A high damping-like effective field per unit current density η_DL up to 40.57 ± 3.32 (Oe/(10⁶ A/cm²)) was observed in the device with a Pt₇₄W₂₆ layer, which is one order of magnitude higher than that in the typical spin-orbit devices with pure heavy metal layer reported in the previous articles. In addition, field-free switching is observed in devices with a wide range of W content using the competing spin currents generated from the Pt_100-xW_x layer. Zero-field switching (ZFS) critical current densities of them are less than 1.09 ± 0.05 (10⁷ A/cm²) with the minimum of 1.58 ± 0.13 (10⁶ A/cm²), indicating the highly efficient field-free spin-orbit switching in the PtW system. Our findings pave the way to high-energy-efficiency spin-orbit devices.