Engineered Continuous Heterogeneous Interfaces in Magnetic‐Dielectric Composites for Low‐Frequency Electromagnetic Wave Absorption

Interface engineering is an effective strategy to strengthen dielectric polarization response and improve electromagnetic (EM) wave absorption performance. Nevertheless, rational design and precise regulation of metal/semiconductor/conductive polymer hybrid heterostructures still pose great challenges. Herein, we skillfully constructed MA/MnO@PEDOT composites (MA = FeCo, CoNi, NiFe) with continuous heterogeneous interfaces via interface engineering. These heterointerfaces spontaneously generate built-in electric fields (BIEFs) that can not only increase the electron density and charge mobility at the interfaces, but also generate dipole polarization, thereby enhancing conductive loss and polarization relaxation. Furthermore, the synergistic effect with magnetic alloy phases with high magnetic permeability can optimize impedance matching, boosting EM energy attenuation across 2-8 GHz. Benefiting from these advantages, the FeCo/MnO@PEDOT composite achieves an effective absorption bandwidth that constitutes 68% of the C band (4-8 GHz), and a minimum reflection loss of -40.15 dB is achieved at 5.36 GHz. Radar cross-section simulation findings clearly indicate that the MA/MnO@PEDOT composites significantly attenuate reflected radar wave and show great potential in practical applications. This work breaks through the limitation that heterogeneous interface design only responds in high-frequency bands, and provides a new idea for preparing EM wave absorption materials with multiple heterogeneous interfaces featuring gradient BIEFs.