Giant Skyrmions Stabilized by Dipole-Dipole Interactions in Thin Ferromagnetic Films

TL;DR

This paper investigates the stabilization of giant skyrmions in thin ferromagnetic films through dipole-dipole interactions, deriving formulas for their size and discussing experimental controllability and observation.

Contribution

It introduces a theoretical model showing how dipole-dipole interactions stabilize giant skyrmions and provides an analytic formula for their radius, linking it to external magnetic fields.

Findings

Dipole-dipole interactions enable stable giant skyrmions in ferromagnetic films.

The skyrmion radius can be controlled by external magnetic fields.

Skyrmions may have been observed as magnetic domains in experiments.

Abstract

Motivated by a recent magnetization reversal experiment on a TbFeCo thin film, we study a topological excitation in the anisotropic nonlinear sigma model together with the Zeeman and magnetic dipole-dipole interactions. Dipole-dipole interactions turn a ferromagnet into a frustrated spin system, which allows a nontrivial spin texture such as a giant skyrmion. We derive an analytic formula for the skyrmion radius. The radius is controllable by the external magnetic field. It is intriguing that a skyrmion may have already been observed as a magnetic domain. A salient feature is that a single skyrmion can be created or destroyed experimentally. An analysis is made also on skyrmions in chiral magnets.