Fe powders coated with Fe₃O₄ insulating layers were synthesized by in-situ oxidization method, and then the Fe/Fe₃O₄ composite cores were prepared by a powder metallurgy procedure. The formation of Fe₃O₄ on the surface of Fe powders can effectively reduce the magnetic loss and enhance the high-frequency performance of magnetic cores. With the increase of pressing pressure, the permeability increased firstly and then decreased, while the magnetic loss shows the opposite law. The residual stress of the composites can be released more sufficient by increasing the annealing temperature, which leads to the increase in permeability; however, Fe₃O₄ will decompose into FeO when the annealing temperature rises to 570 °C, thus destroying the magnetic properties of Fe-based soft magnetic composites. The composite compressed at 800 MPa and annealed in argon at 500 °C for 2 h exhibits excellent magnetic performance, which presents high permeability (μ) of 56 (1 KHz), high saturation magnetization (M_s) of 219.2 emu/g, and low magnetic loss (P) of 30.5 w/kg (20 mT, 100 kHz).

采用原位氧化法合成了包覆有Fe ₃ O ₄绝缘层的Fe粉，然后采用粉末冶金工艺制备了Fe / Fe ₃ O ₄复合芯。在铁粉表面形成Fe ₃ O ₄可以有效降低磁损耗，增强磁芯的高频性能。随着压制压力的增加，磁导率先增大然后减小，而磁损耗却呈现相反的规律。通过提高退火温度，可以更充分地释放复合材料的残余应力，从而提高磁导率。但是，Fe ₃ O ₄退火温度升至570°C时会分解成FeO，从而破坏了铁基软磁复合材料的磁性能。在800 MPa下压缩并在500°C的氩气中退火2 h的复合材料表现出出色的磁性能，表现出56（1 KHz）的高磁导率（μ），219.2 emu / g的高饱和磁化强度（M _s）和30.5 w / kg（20 mT，100 kHz）的低磁损耗（P）。