Ultralow Electrical Current Driven Field-Free Spin-Orbit Torque Switching of Magnetic Tunnel Junctions by Topological Insulators

Spin-orbit torque-driven magnetic random-access memory (SOT-MRAM) is one of the promising candidates for next-generation memory technologies beyond Moore's law. Due to its separation of writing and reading channels, the 3-terminal device design significantly improves the device endurance of SOT-MRAM. However, two major challenges still exist for the perpendicular SOT-MRAM: the ultrahigh writing current density and the need for an external magnetic field to achieve deterministic switching. In this work, a 3-terminal SOT-MRAM device is demonstrated that integrates topological insulators (TIs) by perpendicular magnetic tunnel junction (pMTJ). The giant spin-orbit torque generated by spin-momentum-locked topological surface states significantly reduces the switching current density to as low as 3.0 × 10⁵ A cm⁻². The double magnetic layers with different saturation magnetizations are employed as the recording layer of TIs-pMTJ. Therefore, non-collinear canted magnetic states are generated during the current-driven SOT. By breaking the chiral symmetry of these states through interlayer Dzyaloshinskii–Moriya interaction (DMI), the field-free deterministic SOT switching is achieved. This work demonstrates the topological insulator-driven magnetic field-free SOT-MRAM with ultralow writing density, inspiring the revolution of SOT-MRAM technology from classical to quantum materials.