Field-free magnetization reversal by dual spin-orbit torque

Spin-orbit torque （SOT） has emerged as an effective tool in the manipulation of magnetization in ferromagnetic heterostructures via electric currents, offering a promising pathway for innovative magnetic random-access memory (MRAM) technologies. However, deterministic SOT switching of magnetization in magnetic layers with perpendicular magnetic anisotropy requires an external magnetic field to break the symmetry. Due to the practical difficulties in applying the external magnetic field, it is essential to develop an effective field-free SOT switching mechanism. In this study, we propose a novel four-terminal SOT device model that employs a dual SOT collaborative method applying two orthogonal current pulses simultaneously to break the symmetry. We achieve field-free magnetization switching with a sub-ns switching speed and ultra-low power consumption in the femtojoule range, along with a zero writing error rate. Our model offers a breakthrough for realizing highly efficient field-free switching in SOT MRAM and advancing memory technologies.