Enhanced electromagnetic wave absorption performance by introducing exchange bias in a CIP@γ-FeOOH heterostructure

High-performance electromagnetic wave (EMW) absorbing materials are urgently needed to mitigate electromagnetic (EM) pollution. Carbonyl iron powder (CIP), a conventional magnetic loss absorber, often shows limited absorption bandwidth at low filler loadings. Here, we report a transition-layer-guided oxidation strategy to construct a hierarchical CIP@γ-FeOOH core-shell absorber. A sacrificial SiO₂ shell enables the uniform growth of a flower-like γ-FeOOH shell while protecting the CIP core. The resultant ferromagnetic/antiferromagnetic (FM/AFM) interface induces a significant exchange bias effect, enhancing magnetic loss via interfacial pinning and strengthening the low-frequency magnetic response. Combined with defect-induced polarization and structural scattering, the composite breaks the Snoek's limit constraint with a maximum effective absorption bandwidth (EAB_max) of 6.13 GHz (9.38-15.51 GHz) and a minimum reflection loss (<i>RL</i> _min) of -17.68 dB at 60 wt. %. These findings provide a structural and mechanistic basis for designing CIP-based EMW absorbers with improved broadband performance through interfacial engineering.