Bubble domains in disc-shaped ferromagnetic particles

TL;DR

This paper investigates the stable magnetic states of disc-shaped ferromagnetic particles, identifying a novel bidomain state that remains stable at zero bias field and analyzing how size and external fields influence these configurations.

Contribution

It introduces and characterizes a stable bidomain magnetic state in disc-shaped particles, expanding understanding beyond the traditional monodomain model.

Findings

Bidomain state exists and is stable at zero bias field.

Critical radius for transition depends on film thickness.

Bidomain state remains stable over a range of external fields.

Abstract

We study the fundamental magnetic states of disc-shaped ferromagnetic particles with a uniaxial anisotropy along the symmetry axis. Besides the monodomain, a bidomain state is also identified and studied both numerically and theoretically. This bidomain state consists of two coaxial oppositely magnetized cylindrically symmetric domains and remains stable even at zero bias field, unlike magnetic bubbles in ferromagnetic films. For a given disc thickness we find the critical radius above which the magnetization configuration falls into the bidomain bubble state. The critical radius depends strongly on the film thickness especially for ultrathin films. The effect of an external field is also studied and the bidomain state is found to remain stable over a range of field strengths.