LAUSR

Fe powders coated with Fe 3 O 4 insulating layers were synthesized by in-situ oxidization method, and then the Fe/Fe 3 O 4 composite cores were prepared by a powder metallurgy procedure. The formation of Fe 3 O 4 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, Fe 3 O 4 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).