Fabrication and magnetic performance of Fe@Fe ₃ O ₄ /PVDF soft magnetic composite

Abstract Soft magnetic composites (SMCs) are magnetic materials composed of ferromagnetic cores with insulating coatings that minimize eddy current losses, making them attractive for high‐frequency electronic applications. This work reports a new strategy for fabricating SMCs based on Fe@Fe 3 O 4 core–shell particles combined with a polyvinylidene fluoride (PVDF) binder using low‐temperature cold sintering, without high‐temperature annealing. The Fe 3 O 4 shell provides electrical insulation while maintaining the high magnetization of Fe, and the addition of PVDF enhances compaction and further increases resistivity. Structural characterization confirmed the successful formation of the Fe@Fe 3 O 4 phase. The results show that small PVDF additions improve density and hardness, whereas excessive PVDF causes phase separation and reduces mechanical strength. From a magnetic and electrical standpoint, PVDF incorporation decreases saturation magnetization (196 emu/g at 0% to 157 emu/g at 20%) but greatly suppresses eddy current loss, down to 12 mW/cm 3 at 100 kHz, with resistivity rising to ∼8500 mΩ cm. The optimal balance occurs at 7.5% PVDF, giving M s = 181 emu/g and total loss of 235.1 mW/cm 3 at 100 kHz. These results highlight Fe@Fe 3 O 4 /PVDF composites as promising candidates for high‐frequency magnetic applications requiring low core loss.