Spontaneous square vs. hexagonal nanoscale skyrmion lattices in Fe/Ir(111)

TL;DR

This study uses density functional theory to explore the formation and stability of different skyrmion lattice structures in Fe monolayers on Ir(111), revealing the importance of various magnetic interactions.

Contribution

It demonstrates that the interplay of exchange interactions and Dzyaloshinskii-Moriya interaction determines the lattice symmetry and collinearity of skyrmion states in Fe/Ir(111).

Findings

Fcc-Fe/Ir(111) hosts a square nanoskyrmion lattice.

Hcp-Fe/Ir(111) favors a nearly collinear multi-Q state over a hexagonal skyrmion lattice.

The magnetic interactions crucially influence the symmetry and stability of the skyrmion lattices.

Abstract

We study the emergence of spontaneous skyrmion lattices in an Fe monolayer in fcc and hcp stacking on the Ir(111) surface using density functional theory (DFT). For fcc-Fe/Ir(111) we find the well-known square nanoskyrmion lattice. However, for hcp-Fe/Ir(111) the hexagonal skyrmion lattice previously proposed based on experiments is energetically unfavorable with respect to a hexagonal multi-Q state with nearly collinear magnetic moments. By mapping our DFT calculations to an atomistic spin model we demonstrate that the interplay of pair-wise exchange, higher-order exchange, and Dzyaloshinskii-Moriya interaction is decisive for the symmetry and collinearity of the obtained spin lattice.