Skyrmions at the edge: Confinement effects in Fe/Ir(111)

TL;DR

This study investigates how lateral confinement influences the arrangement of nanoskyrmions in Fe/Ir(111) using microscopy and simulations, revealing edge effects, domain formation, and the role of entropy and pinning.

Contribution

It demonstrates the impact of confinement and edge interactions on skyrmion lattice configurations, supported by combined experimental and Monte-Carlo simulation analysis.

Findings

Strong coupling of magnetic unit cell diagonal to edges

Mismatching symmetries cause frustration and multi-domain states

Simulations explain the stability of multi-domain configurations

Abstract

We have employed spin-polarized scanning tunneling microscopy and Monte-Carlo simulations to investigate the effect of lateral confinement onto the nanoskyrmion lattice in Fe/Ir(111). We find a strong coupling of one diagonal of the square magnetic unit cell to the close-packed edges of Fe nanostructures. In triangular islands this coupling in combination with the mismatching symmetries of the islands and of the square nanoskyrmion lattice leads to frustration and triple-domain states. In direct vicinity to ferromagnetic NiFe islands, the surrounding skyrmion lattice forms additional domains. In this case a side of the square magnetic unit cell prefers a parallel orientation to the ferromagnetic edge. These experimental findings can be reproduced and explained by Monte-Carlo simulations. Here, the single-domain state of a triangular island is lower in energy, but nevertheless multi-domain states occur due to the combined effect of entropy and an intrinsic domain wall pinning arising from the skyrmionic character of the spin texture.