Skyrmions Near Defects

TL;DR

This paper investigates how defects influence skyrmions in thin magnetic films, demonstrating attraction, deformation, and transformation of skyrmions near defects through numerical and analytical methods.

Contribution

It provides a detailed analysis of skyrmion-defect interactions, including deformation and transformation, using micromagnetic energy calculations and solving Landau-Lifshitz-Gilbert and Thiele equations.

Findings

Skyrmions are attracted to defects in thin films.

Deformation of skyrmions increases near phase boundaries.

Skyrmions can transform into snake-like domains near defects.

Abstract

We study the impact of an exchange-reducing defect on a skyrmion for a thin film of finite thickness. Attraction of the skyrmion to a defect is demonstrated in a lattice model by computing the micromagnetic energy accounting for the exchange, Dzyaloshinskii-Moriya interaction, magnetic anisotropy, and dipole-dipole coupling. The spiraling dynamics of the skyrmion towards the defect is illustrated by solving numerically the full Landau-Lifshitz-Gilbert equations on a lattice and, independently, the Thiele equation, with the two methods in agreement with each other. We find that the skyrmion deforms when approaching the defect. Deformation is small in the parameter space far from the phase boundary that determines stability of skyrmions. It increases dramatically near the phase boundary, leading to the transformation of the skyrmion by the defect into a snake-like magnetic domain.