The Effect of Defects on Magnetic Droplet Nucleation

TL;DR

This paper investigates how defects influence magnetic droplet nucleation in two-dimensional systems, adapting classical theory and validating predictions with Monte Carlo simulations, highlighting finite-size and defect effects on metastable transitions.

Contribution

It extends classical nucleation theory to include defect effects and analyzes finite-size impacts on droplet formation in magnetic systems.

Findings

Defects alter free energy barriers and critical droplet size.

Monte Carlo simulations confirm theoretical predictions.

Finite-size effects significantly influence the spinodal line.

Abstract

Defects and impurities strongly affect the timing and the character of the (re)ordering or disordering transitions of thermodynamic systems captured in metastable states. In this paper we analyze the case of two-dimensional magnetic systems. We adapt the classical JMAK theory to account for the effects of defects on the free energy barriers, the critical droplet area and the associated metastable time. The resulting predictions are successfully tested against the Monte-Carlo simulations performed by adopting Glauber dynamics, to obtain reliable time-dependent results during the out-of-equilibrium transformations. We also focus on finite-size effects, and study how the spinodal line (separating the singledroplet from the multi-droplet regime) depends on the system size, the defect fraction, and the external field.