Laboratoire de Physique Théorique
Toulouse - UMR 5152

We present a numerical and theoretical study that supports and explains experimental results on anomalous magnetization fluctuations observed in a uniaxial ferromagnetic film which is forced by an oscillating field to which is added a constant bias field. We perform numerical Monte Carlo simulations of a 2D kinetic Ising model and analyze the data using a droplet model of metastable decay. Our results clearly show that the experimental results are not due to any residual magnetostatic interactions. We find that the origin of the anomalous magnetization fluctuations are not a a critical phenomenon associated with a phase transition. Rather it is a stochastic-resonance phenomena that have no counterpart in the corresponding thermodynamic phase transition, providing a reminder that the equivalence between the dynamical phase transition to an equilibrium phase transition is only valid near the critical region.