On the relaxation of simple magnetic systems

The relaxation at constant applied field and temperature of a simple magnetic system is evaluated in the framework of the micromagnetic approximation and using a Monte Carlo algorithm. Our results, and particularly, those corresponding to the time evolution of the probability of magnetic moment reversal, evidence remarkable differences with the classical Arrehnius-Neel predictions. These differences are linked to the fact that relaxation proceeds through the formation of structures involving a large number of degrees of freedom. (C) 1996 American Institute of Physics.