Dipolar-glass behaviour of an insulating film containing nanogranular Fe particles

We perform Metropolis Monte Carlo simulations of the behaviour of a film of insulating material containing a distribution of magnetic nanoparticles. We assume that these particles only interact through dipolar forces and we find that their behaviour at low T shows characteristics of a spin-glass with a freezing T_f at which the linear susceptibility and the specific heat show a maximum. We obtain the spin glass order parameter as a function of temperature and we also calculate the time auto-correlation of the spin at the center of the system. We find that these results are consistent with the temperature dependence of the variance and the mean of the local field at the central spin.