This paper presents a study regarding the cobalt ferrite obtaining in the CoxFe3-xO4 system, where x = 0.5; 1.0; 1.5 by two different synthesis methods. The Co(II) and Fe(III) complexes method leads to the thermal decomposition at 300 degrees C for this precursor with the pure cobalt ferrite (CoFe2O4) formation for x = 1 or mixed with gamma-Fe2O3 for x = 0.5 and Co3O4 for x = 1.5. By co-precipitation followed by ultrasonic milling synthesis method the pure cobalt ferrite is obtained at 90 degrees C for x = 1 or mixed with Fe3O4 for x = 0.5 and Co3O4 for x = 1.5. When the initial samples are heated at 400 degrees C, the identified oxide phase is identical for the same value of x. The obtained powders were investigated by X-ray diffraction (XRD), FTIR spectrometry and scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDX). The final product has nanometric size and has a strong tendency to agglomerated, thus influencing the saturation magnetization value. The shape of the magnetization curves is influenced by the presence of the secondary phases for x not equal 1. (C) 2012 Elsevier Ltd. All rights reserved.