This paper presents a study for the preparation of CoxFe3−xO4 (x = 0.02, 0.2, 0.5, 0.8, 1.0, 1.1, 1.5) nanoparticles, starting from metal nitrates: Co(NO3)2·6H2O, Fe(NO3)3·9H2O and ethylene glycol (C2H6O2). By heating the solutions metal nitrates-ethylene glycol, the redox reaction took place between the anion NO3− and OH–(CH2)2–OH with formation of carboxylate anions. The resulted carboxylate anions reacted with Co(II) and Fe(III) cations to form
coordinative compounds which are precursors for cobalt ferrite. XRD and magnetic measurements have evidenced the formation
of cobalt ferrite for all studied molar ratios. The average diameter of the cobalt ferrite crystallites was estimated from
XRD data and showed values in the range 10–20 nm. The crystallites size depends on the annealing temperature. The magnetization
of the synthesized samples depends on the molar ratio Co/Fe and on the annealing temperature.