No abstract

We have studied the behavior of the magnetization as a function of temperature of a two-dimensional anisotropic Heisenberg ferromagnetic model within the Green s-function formalism. We have shown that our magnetization curves do not present any plateau in the limit of very small anisotropies, as predicted by the real-space renormalization-group calculations. We compare our results with the recent experimental measurements performed on quasi-two-dimensional films. We also consider the asymptotic spin-wave limit to explain the low-temperature experimental data.