Simultaneous Enhancement of Low‐Frequency Microwave Absorption and Corrosion Resistance in FeSi Alloys via Magnetic‐Structural Heterojunction Engineering

Abstract Soft magnetic alloys, featured with high permeability, hold significant potential in low‐frequency electromagnetic wave absorption. However, the limitations of narrow absorbing bandwidth and susceptibility to corrosion restrict their extensive application. Here, this work demonstrates a joint magnetic‐structural strategy in FeSi alloys, successfully addressing this challenge. Through a typical process of inducing flaky‐shape anisotropy and bidirectional Mott–Schottky heterojunctions, the low‐frequency microwave absorption of the FeSi alloys is effectively reinforced. The minimum reflection loss (RL min ) achieves −43 dB, with the effective absorption bandwidth (EAB, defined as RL < −10 dB) spanning up to 4.1 GHz in S/C bands. Meanwhile, the corrosion resistance is essentially improved with a significant reduction of the corrosive current (I corr ) from 3.984 to 0.427 µA cm −2 in 5 wt.% NaCl/H 2 O solution. The enhanced performance originates from the planar configuration extends the permeability beyond the Snoek limit for improved GHz magnetic loss and the bidirectional Mott–Schottky heterointerfaces regulate interfacial charge distribution, amplifying interfacial polarizations and forming passivation layers for corrosion inhibition. Theoretical modeling confirms that Mn 3 O 4 ‐mediated charge redistribution optimizes impedance matching by balancing permittivity and permeability. This work establishes a feasible method for regulating low‐frequency magnetic/dielectric parameters for enhance electromagnetic attenuation and environmental durability in magnetic alloy absorbents.