Influence of heat treatment on microstructures and magnetic properties of Fe-based soft magnetic composites prepared by co-precipitation method

•Fe particles were coated with a uniform (NiZn)Fe2O4 via a co-precipitation method.•With the increase of heat treatment temperature, the O element in the boundary gradually penetrated into the Fe matrix.•With the increase of heat treatment temperature, the internal stress release of the sample is more complete.•The 450 °C argon-annealed sample had the optimum magnetic properties (u = 55.8, Pcv = 12.2 kw/m3, Hc = 22.6 A/m).