A series of Fe₂O₃-SiO₂ nanocomposites (25 weight % of Fe₂O₃) has been prepared using a sol-gel method. Samples showing different features were obtained by varying the evaporation conditions acting on the surface / volume ratio of the starting sol. The samples were investigated using Mössbauer spectroscopy at low temperature. The Fe₂O₃ nanoparticles have been identified as maghemite ( γ-Fe₂O₃) particles. The samples show a superparamagnetic behavior with a blocking temperature that depends on the average particle size.