Nano‐Heterointerface Coupling Engineering Induced Electromagnetic Response by Tailored Spindle Arrays for Microwave Absorption

Abstract Heterointerface coupling engineering derived from nanoscale heterostructures represents a promising approach to developing high‐performance electromagnetic functional materials, but the underlying mechanism of the heterointerface coupling for microwave absorption remains unclear. In this work, nano‐interfaces and dielectric/magnetic heterostructures are designed and customized in multilevel spherical architecture with graphitized carbon core and Fe ₃ O ₄ shell (C/Fe ₃ O ₄ ) in tailored spindle arrays by an in situ reduction process. Results from electron holography and COMSOL multiphysics simulation demonstrate that high‐density nano‐interfaces exhibit impressive heterointerface coupling and induce strong polarization relaxation. The spatial distribution of Fe ₃ O ₄ nanoparticles constructs multiscale magnetic coupling networks, which enhance interactions with incident microwaves and improve magnetic loss capability. Furthermore, the coupling mechanisms of the dielectric/magnetic heterostructures and heterointerface for the microwave absorption are systematically investigated. The as‐prepared C/Fe ₃ O ₄ spherical heterostructures exhibit remarkable electromagnetic absorption performance, achieving a maximum refection loss of ‐40.1 dB and an effective absorption bandwidth of 5.12 GHz at a thickness of 2.0 mm. This finding not only reveals the intrinsic loss mechanisms of nano‐heterointerface coupling but also provides a new strategy for constructing multilevel hollow heterostructures.