The skyrmion-bubble transition in a ferromagnetic thin film

TL;DR

This paper develops an analytical model to study the transition between skyrmions and bubbles in ferromagnetic thin films, revealing conditions for coexistence, transformation, and size tuning of these topological solitons.

Contribution

The work introduces a new analytical framework to describe the skyrmion-bubble transition and identifies a critical point where the energy barrier disappears, allowing continuous size tuning.

Findings

Coexistence region of skyrmions and bubbles identified.

Transformations between skyrmions and bubbles occur near the coexistence region.

Size of the topological solitons can be tuned from micrometer to nanometer with magnetic field.

Abstract

Magnetic skyrmions and bubbles, observed in ferromagnetic thin films with perpendicular magnetic anisotropy, are topological solitons which differ by their characteristic size and the balance in the energies at the origin of their stabilisation. However, these two spin textures have the same topology and a continuous transformation between them is allowed. In the present work, we derive an analytical model to explore the skyrmion-bubble transition. We evidence a region in the parameter space where both topological soliton solutions coexist and close to which transformations between skyrmion and bubbles are observed as a function of the magnetic field. Above a critical point, at which the energy barrier separating both solutions vanishes, only one topological soliton solution remains, which size can be continuously tuned from micrometer to nanometer with applied magnetic field.