Edge domain walls in ultrathin exchange-biased films

TL;DR

This paper analyzes edge domain walls in ultrathin exchange-biased ferromagnetic films, introducing a micromagnetic model and characterizing the behavior of energy minimizers in various geometries.

Contribution

It develops a two-dimensional micromagnetic energy model for exchange-biased films and characterizes the minimizers, including a simplified algebraic model for large samples.

Findings

Energy minimizers are one-dimensional and do not wind.

The algebraic model describes interior and boundary magnetization behavior.

Asymptotic results hold for finite rectangular samples.

Abstract

We present an analysis of edge domain walls in exchange-biased ferromagnetic films appearing as a result of a competition between the stray field at the film edges and the exchange bias field in the bulk. We introduce an effective two-dimensional micromagnetic energy that governs the magnetization behavior in exchange-biased materials and investigate its energy minimizers in the strip geometry. In a periodic setting, we provide a complete characterization of global energy minimizers corresponding to edge domain walls. In particular, we show that energy minimizers are one-dimensional and do not exhibit winding. We then consider a particular thin film regime for large samples and relatively strong exchange bias and derive a simple and comprehensive algebraic model describing the limiting magnetization behavior in the interior and at the boundary of the sample. Finally, we demonstrate that the asymptotic results obtained in the periodic setting remain true in the case of finite rectangular samples.