Curvature induced drift and deformation of magnetic skyrmions: comparison of ferro- and antiferromagnetic cases

TL;DR

This paper theoretically investigates how the curvature of chiral magnetic films influences the static and dynamic behavior of skyrmions, revealing curvature-induced drift effects that depend on skyrmion type and magnetic ordering.

Contribution

It provides a comparative analysis of curvature effects on ferromagnetic and antiferromagnetic skyrmions, including analytical models and numerical validation.

Findings

Curvature induces a drift of skyrmions without external stimuli.

Neel skyrmions experience a linear force proportional to curvature gradient.

Bloch skyrmions are less affected and deform more during motion.

Abstract

The influence of the geometrical curvature of chiral magnetic films on the static and dynamic properties of hosted skyrmions are studied theoretically. We predict the effects of the curvature-induced drift of skyrmions under the action of the curvature gradients without any external stimuli. The strength of the curvature-induced driving force essentially depends on the skyrmion type, Neel or Bloch, while the trajectory of motion is determined by the type of magnetic ordering: ferro- or antiferromagnetic. When moving on the surface, skyrmions undergo deformations that depend on the type of skyrmion. In the small-curvature limit, using the collective-variable approach we show, that the driving force acting on a Neel skyrmion is linear in the gradient of the mean curvature. The driving acting on a Bloch skyrmion is much smaller: it is proportional to the product of the mean curvature and its gradient. In contrast to the fast Neel skyrmions, the dynamics of the slow Bloch skyrmions is essentially affected by the skyrmion profile deformation. For the sake of simplicity, we restrict ourselves to the case of zero Gaussian curvature and consider cylindrical surfaces of general type. Equations of motion for ferromagnetic and antiferromagnetic skyrmions in curved magnetic films are obtained in terms of collective variables. All analytical predictions are confirmed by numerical simulations.