Disorder effects on the metastability of classical Heisenberg ferromagnets

TL;DR

This study explores how disorder influences the reversal time of classical Heisenberg ferromagnets, revealing complex dependencies on anisotropy, temperature, and external fields through Monte Carlo simulations.

Contribution

It provides new insights into the effects of different types of anisotropy disorder on reversal time in classical Heisenberg ferromagnets, including scaling behaviors.

Findings

Reversal time increases with anisotropy strength in pure systems.

Disorder effects on reversal time depend on temperature and distribution type.

Reversal time exhibits non-monotonic behavior with distribution width for normal anisotropy.

Abstract

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 $\tau h_z^{n} \sim f(h_x)$.