Spirals and skyrmions in antiferromagnetic triangular lattices

TL;DR

This paper investigates the formation and stability of spirals and skyrmions in two-dimensional antiferromagnetic triangular lattices on inversion-symmetry-breaking substrates, using first-principles calculations and simulations to explore material realizations.

Contribution

It identifies specific material interfaces capable of hosting skyrmion and spiral phases, highlighting the role of weak Dzyaloshinskii-Moriya interactions and magnetic anisotropy in stabilizing these structures.

Findings

Skyrmion lattices can form with weak Dzyaloshinskii-Moriya interactions.

Magnetic anisotropy influences skyrmion stability, with easy-plane anisotropy being beneficial.

Certain interfaces like Cr/MoS2 and Fe/WSe2 can host spin spirals and skyrmion lattices.

Abstract

We study realizations of spirals and skyrmions in two-dimensional antiferromagnets with a triangular lattice on an inversion-symmetry-breaking substrate. As a possible material realization, we investigate the adsorption of transition-metal atoms (Cr, Mn, Fe, or Co) on a monolayer of MoS$_2$, WS$_2$, or WSe$_2$ and obtain the exchange, anisotropy, and Dzyaloshinskii-Moriya interaction parameters using first-principles calculations. Using energy minimization and parallel-tempering Monte-Carlo simulations, we determine the magnetic phase diagrams for a wide range of interaction parameters. We find that skyrmion lattices can appear even with weak Dzyaloshinskii-Moriya interactions, but their stability is hindered by magnetic anisotropy. However, a weak easy plane magnetic anisotropy can be beneficial for stabilizing the skyrmion phase. Our results suggest that Cr$/$MoS$_2$, Fe$/$MoS$_2$, and Fe$/$WSe$_2$ interfaces can host spin spirals formed from the 120$^{\circ}$ antiferromagnetic states. Our results further suggests that for other interfaces, such as Fe$/$MoS$_2$, the Dzyaloshinskii-Moriya interaction is strong enough to drive the system into a three-sublattice skyrmion lattice in the presence of experimentally feasible external magnetic field.