Efficient Spin–Orbit Torque Switching via Spin‐Vorticity Coupling Effect in Light‐Metal/Ferromagnetic‐Metal Bilayers

ABSTRACT Developing highly efficient spin–orbit torques based on light metal materials is crucial for achieving low‐power and cost‐effective spintronic devices. By utilizing longitudinal second‐harmonic resistance as a sensitive probe, here we report an efficient field‐free in‐plane magnetization switching enabled by the spin‐vorticity coupling effect in PtCo/Cu bilayer structures. Compared to conventional heavy‐metal Pt‐based systems, the critical switching electric field is reduced by 79% (with a power consumption reduction of approximately 46%) through increasing the Cu layer thickness. This reduction is attributed to the enhanced mobility transition within the composition gradient region at the interface. Moreover, we establish that the critical switching electric field exhibits an inverse‐square dependence on Cu conductivity, consistent with the behavior of SVC conductivity. Our research findings highlight the potential of highly conductive light metals in developing low‐power, high‐efficiency spintronic devices.