Abstract: Ferromagnetic absorbing materials (FAMs) are essential for electromagnetic radiation mitigation, signal interference suppression, and military stealth applications. However, with the growing complexity of the electromagnetic environment, the development of FAMs that simultaneously exhibit strong microwave absorption in the 2-8 GHz range and maintain efficient signal transmission remains a significant challenge. To address this challenge, a facile surface micro-oxidation followed by phosphorization/selenization was employed to construct a novel multi-heterostructure composite, carbonyl iron/Fe₃P/FeSe/Fe₂O₃ (CIPSe). The results revealed that the extraordinarily low-frequency microwave absorption performance was primarily attributed to optimized impedance matching and the synergistic magnetic/dielectric loss enabled by the multi-heterostructure. As a result, CIPSe achieved a minimum reflection loss of -43.04 dB at 4.09 GHz and an effective absorption bandwidth of 1.84 GHz, effectively encompassing critical 5 G communication frequencies from 3.39 to 5.23 GHz. Remarkably, by tuning the matching thickness between 2.0 and 5.0 mm, CIPSe maintained reflection losses below -20 dB-corresponding to over 99 % microwave absorption-across a broad frequency range of 2.60-10.83 GHz. Furthermore, a patch antenna fabricated using CIPSe as the dielectric substrate demonstrated excellent impedance matching characteristics and high gain in the positive direction of the z-axis, confirming high transmission efficiency and its potential for stealth-enabled signal transmission. Overall, this multi-interface engineering strategy provides a promising pathway to advance the design of FAMs by simultaneously achieving high-efficiency microwave absorption and reliable signal transmission, particularly for next-generation electromagnetic applications such as 5 G communication systems.

Key words: Ferromagnetic absorbing materials, Multi-heterostructure, Low-frequency, Microwave absorption, Stealth information transmission