Structural design of magnetic metal-inorganic framework FeNi@SiFeO composite powders and electromagnetic parameter regulation via magnetic field response

To address the synergistic requirements of structural wave-absorbing materials—broadband absorption, low thickness, lightweight, and high mechanical strength—this study constructs a FeNi@SiFeO composite powder with external magnetic field responsiveness through multi-scale structural design. The material features a porous silicon ferrite (SiFeO) framework in which FeNi alloy nanoparticles (approximately 130 nm in diameter) are in situ encapsulated within the pores, forming a core-shell heterostructure. The composite powder exhibits significant structural advantages: a density of 0.73 g/cm³, a specific surface area of 116.37 m²/g, and a saturation magnetization Ms of 57.5 emu/g. Electromagnetic performance tests reveal that in the 0.1–18 GHz frequency range, the real part of the complex permittivity ε′ ranges from 8.0 to 10.0, and the real part of the complex permeability μ′ ranges from 1.1 to 2.3, demonstrating good impedance matching with air. Notably, a dielectric anomaly (ε′ mutation) is observed in the 14.5–16.5 GHz band, attributed to magnetic-electric coupling effects and enhanced interfacial polarization induced by the external magnetic field. Wave-absorbing performance studies indicate that at a material thickness of 2.9 mm, the effective absorption bandwidth (RL ≤ −10 dB) reaches 4.6 GHz in the X-band (6.7–11.25 GHz), with a minimum reflection loss of −42.3 dB at the central frequency of 8.55 GHz. Importantly, magnetic field regulation enables active adaptation of absorption characteristics without altering the composite’s molding process or mechanical properties, offering a novel strategy for developing "structural-functional integrated" smart wave-absorbing materials.