Comparative structural, morphological and magnetic study of MFe2O4 nanopowders prepared by different synthesis routes

Abstract MFe2O4 nanoparticles with M = Fe, Co and Ni were prepared by three different methods (coprecipitation, sol-gel and hydrothermal synthesis). XRD patterns reveal an increase in the unit cell parameter associated to the presence of Fe2+. More intense diffraction maxima are observed for samples prepared by sol-gel. Particle size appears to be larger for Co ferrites and sol-gel samples. By contrast, smaller grain sizes are observed for NiFe2O4 and hydrothermal samples. The highest Ms appears in the Fe3O4 obtained by coprecipitation. An increment in the saturation magnetization values is found in the cobalt and nickel samples prepared by hydrothermal method. Iron and nickel samples behave as superparamagnetic materials with low blocking temperatures while CoFe2O4 samples exhibit a characteristic ferrimagnetism. Variations observed in the ZFC/FC curves of coprecipitation-prepared samples are related to both the different particle size distribution and the values of magnetic anisotropy constant.