Disorder effects on the metastability of classical Heisenberg ferromagnets

In the present work, we investigate the effects of disorder on the reversal time ($\tau$) of classical anisotropic Heisenberg ferromagnets in three dimensions by means of Monte Carlo simulations. Starting from the pure system, our analysis suggests that $\tau$ 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 $\tau$ with the strength of anisotropy strongly depends on temperature. (ii) At lower temperatures, the decrement in $\tau$ with increasing width of the distribution is more prominent. (iii) For the case of normally distributed anisotropy, the variation of $\tau$ with the width of the distribution is non-monotonic, 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 $\tau$, which appear to obey a scaling behavior of the form $\tau h_z^{n} \sim f(h_x)$.