Degradation of domains with sequential field application

TL;DR

This paper models how alternating magnetic fields cause domain shrinkage and roughness changes in ferromagnetic materials, revealing the role of disorder and initial states in these phenomena.

Contribution

The study introduces a simple scalar-field model that reproduces experimental observations of domain degradation under alternating fields, highlighting the impact of disorder correlation length and initial interface conditions.

Findings

Domains shrink via linear and exponential behaviors.

Roughness exponents match experimental data.

Area loss results from disorder effects and local curvature-induced fields.

Abstract

Recent experiments show striking unexpected features when alternating square magnetic field pulses are applied to ferromagnetic samples: domains show area reduction and domains walls change their roughness. We explain these phenomena with a simple scalar-field model, using a numerical protocol that mimics the experimental one. For a bubble and a stripe domain, we reproduce the experimental findings: The domains shrink by a combination of linear and exponential behavior. We also reproduce the roughness exponents found in the experiments. Our results suggest that the observed effects are due to a change in the disorder correlation length when the domain walls are subject to alternating fields during the first cycles, where the initial state of the interface plays a crucial role. Finally, our simulations explain the area loss by the interplay between disorder effects and effective fields induced by the local domain curvature.