Designing Magnetic Topological Insulator Trilayers for Highly Efficient Spin-Orbit Torque Switching

Spin-orbit torque (SOT) enables efficient electrical control of magnetization, offering a pathway toward low-power spintronic devices. Magnetic topological insulators (TIs), with spin-momentum-locked surface states and intrinsic ferromagnetism, provide a unique platform for switching the edge-current chirality in quantum anomalous Hall (QAH) insulators. Here, we employ molecular beam epitaxy to synthesize a series of magnetic TI trilayers with controlled layer thicknesses on heat-treated SrTiO₃(111) substrates. Electrical transport measurements reveal that SOT-driven magnetization reversal and the associated switching of QAH edge current chirality are governed by a SrTiO₃(111) substrate-induced charging effect, which generates a chemical potential asymmetry between the top and bottom magnetic TI layers. The switching polarity and efficiency are further tuned through heterostructure design, gate voltage, and an in-plane magnetic field. These findings identify chemical-potential asymmetry as the key mechanism for achieving a large SOT switching ratio and establish a route toward electrical control of edge current and QAH-based logic and memory devices.