Transverse instabilities of stripe domains in magnetic thin films with perpendicular magnetic anisotropy

TL;DR

This paper investigates the transverse instabilities of stripe domains in magnetic thin films with perpendicular magnetic anisotropy, revealing mechanisms for skyrmion nucleation through analytical and numerical methods.

Contribution

It provides a detailed analysis of the onset and nonlinear evolution of transverse instabilities in bion stripe domains, including topological and non-topological variants, using an averaged Lagrangian approach.

Findings

Non-topological stripes undergo neck instability leading to droplet chains.

Topological stripes experience snake instability resulting in skyrmion nucleation.

Analytical predictions match numerical simulations for both linear and nonlinear evolution.

Abstract

Stripe domains are narrow, elongated, reversed regions that exist in magnetic materials with perpendicular magnetic anisotropy. Stripe domains appear as a pair of domain walls that can exhibit topology with a nonzero chirality. Recent experimental and numerical investigations identify an instability of stripe domains in the long direction as a means of nucleating isolated magnetic skyrmions. Here, the onset and nonlinear evolution of transverse instabilities for a dynamic stripe domain known as the bion stripe are investigated. Both non-topological and topological variants of the bion stripe are shown to exhibit a long-wavelength transverse instability with different characteristic features. In the former, small transverse variations in the stripe's width lead to a neck instability that eventually pinches the non-topological stripe into a chain of two-dimensional breathers composed of droplet soliton pairs. In the latter case, small variations in the stripe's center results in a snake instability whose topological structure leads to the nucleation of dynamic magnetic skyrmions and antiskyrmions as well as perimeter-modulated droplets. Quantitative, analytical predictions for both the early, linear evolution and the long-time, nonlinear evolution are achieved using an averaged Lagrangian approach that incorporates both exchange (dispersion) and anisotropy (nonlinearity). The method of analysis is general and can be applied to other filamentary structures.