Granular films consisting of finely dispersed Fe2O3grains in an Al2O3matrix have been studied by means of Mo¨ssbauer spectroscopy and magnetization measurements. The temperature dependence of the relaxation time is coherent with the superparamagnetism model only if in the &tgr;0calculation, the noncompensated moment of the antiferromagnetic particles, is considered. This moment is proportional to (n)1/2,nbeing the number of magnetic atoms in the particle.