Microstructural and magnetic properties of core–shell FeSiAl composites with Ni0.4Zn0.45Co0.15Fe2O4 layer by sol–gel method

•FeSiAl magnetic powder cores with different NZCF contents by sol-gel were prepared.•The structures and properties with different contents of NZCF were studied.•Moderate NZCF contents can improve μ’ and Q of FeSiAl composites. FeSiAl/Ni0.4Zn0.45Co0.15Fe2O4 ferrite core–shell particles and cylindrical magnetic cores have been synthesized by sol–gel auto-combustion method. The magnetic cores were prepared by pellet molding process and high temperature annealing at 700 °C for 1 h. The reaction, surface morphology and magnetic properties of FeSiAl/ Ni0.4Zn0.45CoFe2O4 ferrite cores have been investigated by Differential thermal analysis-thermogravimetry (DTA-TG), X-ray diffraction (XRD), the impedance analyzer and Vibration sample magnetometer (VSM). The results indicates that there are three stages to form ferrite. The cores of unphosphated FeSiAl/Ni0.4Zn0.45CoFe2O4 ferrite will be oxidized in air at 700 °C. The spinel ferrites are successfully prepared by sol–gel and form a homogeneous as well as porous structure on the surface of the cores. The maximum permeability is 41 at 6 wt% ferrite. Ms decreases from 106.6 emu/g to 103.6 emu/g, with the increase of ferrite content.