Nitrogen Doping Regulated Hollow Soft‐Magnetic Alloy/Carbon Composites to Break Through Snoek Limit for Total Absorption of Electromagnetic Waves in n77, n78, and n79 of 5G Bands

ABSTRACT The electromagnetic wave (EMW) absorption at low‐frequency range of a material is constrained by the Snock limit due to its low natural resonance frequency ( f r ). Herein, we develop a nitrogen‐doped hollow soft‐magnetic alloy coated carbon composites (CoNi@NC) by enhancement of f r and optimization of impedance matching to break through the Snock limit, fulfilling an EMW absorption in n77 (3.3–4.2 GHz), n78 (3.3–3.8 GHz), and n79 (4.4–5.0 GHz) of the whole 5G bands. The multiple heterogeneous interfaces in our composites are constructed to regulate their dielectric loss ( ε′′ ), and defect engineering is designed to control magnetic loss ( µ′′ ) for the formation of a magnetic‐dielectric synergistic loss system, which significantly enhances the f r and optimizes the impedance matching. Ultimately, it achieves a superior reflection loss of −47.66 dB and a low‐frequency effective absorption bandwidth of 2.21 GHz (2.95–5.16 GHz). Density functional theory calculations reveal that nitrogen atoms could gather electrons at the Fermi level of material and form an asymmetric structure, as well as influence magnetic domains, resulting in a 180% increase in µ′′ of CoNi@NC compared to pure CoNi. This work offers a strategy for preparation of multi‐functional materials to realize EMW absorption application in 5G Terminal.