• • Carbonization at 700°C induces partial phase transformation from Fe3O4 to Fe2SiO4, yielding C/Fe3O4@Fe2SiO4@DC microspheres with RLmin = −17.86 dB at 2.2 mm and EAB = 6.03 GHz (11.5–17.5 GHz); this dual-phase heterointerface strategy outperforms single-phase Fe3O4 or Fe2SiO4 absorbers by broadening effective bandwidth while maintaining moderate thickness, directly addressing industrial needs for thin, broadband EMI suppression in 5G and wireless charging bands.
• • The raspberry-like 3D carbon framework, formed via organic decomposition during carbonization, provides multiple active sites for electromagnetic wave reflection and scattering, prolonging propagation paths; this structural hierarchy enables a 6.03 GHz EAB at only 2.2 mm thickness, a 34% reduction in thickness compared to typical ferrite-based absorbers (≥3.0 mm) while achieving comparable or superior bandwidth, critical for space-constrained electronics.
• • Magnetic nanoparticles within the composite contribute natural resonance, exchange resonance, and eddy current losses, establishing a dual dielectric-magnetic loss mechanism; this synergy yields RLmin = −17.86 dB, which, although moderate in absolute value, is achieved with a broad EAB, indicating balanced impedance matching and attenuation—essential for real-world broadband absorption where high RL at a single frequency often sacrifices bandwidth.
• • The controlled carbothermal process enables precise tuning of phase composition and defect density, with 700°C identified as optimal; deviations in temperature alter the Fe3O4/Fe2SiO4 ratio and carbon graphitization, directly impacting electromagnetic parameters. This process window (700°C) offers a scalable route for manufacturing high-performance absorbers with consistent reproducibility, as evidenced by the stable RLmin and EAB metrics.