Low-frequency microwave absorbing materials have been challenging for many years. Three-dimensional dielectric/magnetic porous materials are beneficial for improving the low-frequency microwave absorbing performance because of natural resonance and improved impedance matching. In this study, Fe₃O₄@C 3D foam was prepared by carbothermal reduction method and the microwave attenuation performances and mechanisms were studied. By adjusting the content of Fe₃O₄@C 3D foam in paraffin composites, the low-frequency microwave attenuation capacity could be effectively optimized. The minimum reflection loss (RL_min) of paraffin composite with 40% (in mass fraction) loading exhibits −54.7 dB at 4.1 GHz for a thickness of 4.0 mm. Surprisingly, the paraffin composite with 50% (in mass fraction) loading could almost cover 2–4 GHz (S-band) in the thickness range of 3.5–5.5 mm. The strong low-frequency microwave attenuation property of Fe₃O₄@C 3D foam is mainly attributed to excellent low-frequency impedance matching, natural resonance, interfacial/dipole polarization, multiple reflection and scattering. This method provides a new perspective for preparing lightweight and high performance low-frequency microwave absorbing materials.

低频微波吸收材料多年来一直具有挑战性。三维介电/磁性多孔材料由于自然共振和改进的阻抗匹配而有利于提高低频微波吸收性能。本研究采用碳热还原法制备了Fe ₃ O ₄ @C 3D泡沫，并研究了其微波衰减性能和机理。通过调整石蜡复合材料中Fe ₃ O ₄ @C 3D泡沫的含量，可以有效优化低频微波衰减能力。最小反射损耗（RL _min）具有 40%（质量分数）负载的石蜡复合材料在 4.1 GHz 下显示 −54.7 dB，厚度为 4.0 mm。令人惊讶的是，具有 50%（质量分数）负载的石蜡复合材料几乎可以在 3.5-5.5 mm 的厚度范围内覆盖 2-4 GHz（S 波段）。_{Fe 3} O ₄ @C 3D泡沫的强低频微波衰减特性主要归因于优异的低频阻抗匹配、自然共振、界面/偶极极化、多次反射和散射。该方法为制备轻质高性能低频吸波材料提供了新的视角。