Disorder effects on the metastability of classical Heisenberg ferromagnets.

Abstract

In the present paper, we investigate the effects of disorder on the reversal time (τ) of classical anisotropic Heisenberg ferromagnets in three dimensions by means of Monte Carlo simulations. Starting from the pure system, our analysis suggests that τ increases with increasing anisotropy strength. On the other hand, for the case of randomly distributed anisotropy, generated from various statistical distributions, a set of results is obtained: (i) For both bimodal and uniform distributions, the variation of τ with the strength of anisotropy strongly depends on temperature. (ii) At lower temperatures, the decrement in τ with increasing width of the distribution is more prominent. (iii) For the case of normally distributed anisotropy, the variation of τ with the width of the distribution is nonmonotonic, featuring a minimum value that decays exponentially with the temperature. Finally, we elaborate on the joint effect of longitudinal (h_{z}) and transverse (h_{x}) fields on τ, which appear to obey a scaling behavior of the form τh_{z}^{n}∼f(h_{x}).