The bismuth substituted cobalt ferrite CoBixFe₂-xO₄ (x = 0.1) were synthesized by co-precipitation procedure. The properties of the samples were controlled by heat treatment through annealing processes at temperatures of 300⁰C, 400⁰C, and 500⁰C. After that, all samples were characterized by XRD, FTIR, and VSM. The high purity fcc inverse spinel with Fd-3 space group is obtained following the Rietveld refinement of XRD. The spectrum analysis in the range 400-600 cm-1 confirms the spinel ferrite structure. The net magnetic moment nB, coercive field HC, and magnetization saturation MS of the co-precipitated bismuth substituted cobalt ferrite samples increase with increasing annealing temperature which attributes to the increase of the anisotropy constant.
