Chemical synthesis of Fe/Fe_3O_4 core-shell composites with enhanced soft magnetic performances

摘要

The large-grain Fe/Fe_3O_4 composite particles with average size of about 1.2 µm have been fabricated by a facile one-step solvothermal method. The formation of high-purity Fe_3O_4 as the shells (90.14 wt%) and α-Fe as the cores (9.86 wt%) in the Fe/Fe_3O_4 composites leads to their high saturation magnetization of 119.6 A m~2 Kg~(-1). Very low coercivity of 30 Oe is obtained in the composites due to their uniform cubic-shaped morphologies. Compared with Fe-based nanosized particles, these micron-sized magnetic Fe/Fe_3O_4 composites exhibit high air stability and good compactibility with high compressed density of 5.9 g cm~(-3). The fully compacted sample shows good soft magnetic properties including high magnetic induction B_(1.2k (H=1200 A/m)) of 540 mT and good frequency-dependent magnetic properties with operating frequency up to 50 MHz superior to those of the most traditional soft magnetic ferrites, which promotes their potential applications in high-frequency and high-power magnetic devices.