Tunable microwave absorption in layered antiferromagnetic topological insulator MnBi ₂ Te ₄ via progressive defect engineering

As an intrinsic magnetic topological insulator, MnBi₂Te₄ (MBT) has garnered significant attention owing to its unique magnetic and topological properties. However, the mechanism by which oxygen-doping modulates the transport properties in MBT remains unclear. The electromagnetic wave (EMW) absorption performance of MBT and the related attenuation mechanism lack clarification. Here, a progressive oxygen regulation strategy is proposed for MBT for the first time, achieving broad high-frequency EMW attenuation at small thickness. The EMW attenuation performance is synergistically manipulated by multiple factors, such as morphology, defect and conductivity, which significantly enhances its polarization loss and optimizes impedance matching. It is demonstrated that the extent of oxidation doping (i.e., the number of oxidized layers and types of oxidized bonds) significantly influences its intrinsic conductivity and polarization loss. Accordingly, the surface oxidized MBT exhibited an effective absorption bandwidth of 3.63 GHz (1.31 mm thickness), representing a 61% enhancement compared to the pristine MBT. Furthermore, the radar cross section is reduced by -25 dB across an ultra-wide angular range of -90–90°. This work not only elucidates the distinct role of oxidative doping in modulating the intrinsic conductivity and EMW absorption, but also provides a feasible strategy for mitigating electromagnetic interference via MBT.