Ultralight Medium‐Entropy Alloy/CNT Aerogels With Synergistic Magnetoelectric Coupling for Enhanced Low‐Frequency Microwave Absorption

Low‐frequency (2–6 GHz) microwave absorption materials are urgently required for radar stealth and electronic warfare systems; however, traditional materials struggle to balance low‐frequency absorption, broadband capability, and lightweight properties. To overcome these limitations, a novel medium‐entropy NiCoFe magnetic alloy aerogel/carbon nanotube (CNT) composite was prepared via self‐propagating combustion followed by one‐step reduction/catalytic growth. The material features a 3D porous skeleton and an ultralow density (32 mg cm −3 ) and exhibits exceptional microwave absorption performance, including a minimum reflection loss (RL) of −56.5 dB, an effective absorption bandwidth (EAB) of 5.2 GHz, and a 3.6 GHz low‐frequency attenuation coverage within the 2–6 GHz band under the auxiliary RL < −4 dB cutoff. Electromagnetic parameter analysis indicates that the excellent performance stems from synergistic dielectric and magnetic losses. Crucially, X‐ray absorption spectroscopy (XAS) and micromagnetic simulations support a mechanism in which short‐range ordering (SRO)—defined here as the preferential, nonrandom distribution of constituent atoms within the face‐centered cubic (FCC) lattice shells—is consistent with nonuniform local magnetic anisotropy (LMA) and enhanced spin rotational relaxation as a magnetic loss mechanism. This “SRO–LMA–magnetic loss” mechanism, realized within the 3D magnetoelectric‐coupling structure, offers an effective route for designing ultralight, low‐frequency microwave absorbers.