Competitive metastable behaviours of surface and bulk in Ising ferromagnet

TL;DR

This study investigates the surface and bulk magnetization reversal in a 3D Ising ferromagnet using Monte Carlo simulations, revealing how the relative surface-core interaction influences reversal times and identifying a critical interaction strength with scaling behavior.

Contribution

It introduces a detailed analysis of surface and bulk reversal dynamics in Ising ferromagnets, including a new scaling relation for the critical interaction strength based on temperature and magnetic field.

Findings

Surface reversal can be faster or slower than bulk depending on interaction strength.

A critical interaction strength ($R_c$) equalizes surface and bulk reversal times.

The critical interaction strength scales with temperature and magnetic field as $R_c \\sim h^{-eta}f(Th^{\\alpha})$.

Abstract

The reversal of magnetisation has been studied in a three dimensional Ising ferromagnet by Monte Carlo simulation with Metropolis single spin flip algorithm using random updating scheme. The outer layers are considered as surface. The surface interacts with core with a relative ferromagnetic interaction strength. Depending on the relative interaction strength, the time of reversal of the surface was found to be different from that of the bulk. For weaker relative strength, surface reversal was found to be faster than that of bulk and vice versa for stronger relative interaction strength. A critical value ($R_c$) of relative interaction strength provides same time of reversal of surface and bulk. This critical relative interaction strength was found to be a function of the temperature ($T$) and applied magnetic field ($h$). The scaling relation $R_c \sim h^{-\beta}f(Th^{\alpha})$, where, $\alpha=0.23\pm0.01$ and $\beta = -0.06\pm0.01$, has been proposed, numerically by the method of data collapse. The metastable volume fractions, for both surface and bulk, were found to follow the Avrami's law. The critical relative interaction strength ($R_c$) has been observed to decrease in an exponential ($e^{bL^{-1.5}})$ fashion with the system size ($L$).