AC Current‐Driven Magnetization Switching and Nonlinear Hall Rectification in a Magnetic Topological Insulator

Spin–orbit torque arising from the spin–orbit‐coupled surface states of topological insulators enables current‐induced control of magnetization with high efficiency. Here, alternating‐current (AC) driven magnetization reversal is demonstrated in a semi‐magnetic topological insulator (Cr,Bi,Sb) 2 Te 3 /(Bi,Sb) 2 Te 3 , facilitated by a low threshold current density of 1.5 × 10 9 A m −2 . Time‐domain Hall voltage measurements using an oscilloscope reveal a strongly nonlinear and rectified Hall response during the magnetization reversal process. Fourier analysis of the time‐varying Hall voltage identifies higher‐harmonic signals and a rectified direct‐current (DC) component, highlighting the complex interplay among the applied current, external magnetic field, and magnetization dynamics. Furthermore, a hysteretic behavior in the current‐voltage characteristics gives rise to frequency mixing under dual‐frequency excitation. This effect, distinct from conventional polynomial‐based nonlinearities, allows for selective extraction of specific frequency components. The results demonstrate that AC excitation can not only switch magnetization efficiently but also induce tunable nonlinear responses, offering a new pathway for multifunctional spintronic devices with potential applications in energy‐efficient memory, signal processing, and frequency conversion.