Spin Spirals in Surface Alloys on Ru(0001): A First-principles Study

TL;DR

This study uses first-principles calculations to reveal that surface alloy systems FeAu₂/Ru(0001) and MnAu₂/Ru(0001) favor left-rotating spin spirals driven by Dzyaloshinskii-Moriya interactions, with notable magnetic anisotropy.

Contribution

First-principles analysis of magnetic ground states in surface alloys on Ru(0001), highlighting the role of substrate in stabilizing spin spirals and magnetic anisotropy.

Findings

Spin spirals are energetically favored over ferromagnetic states.

The Dzyaloshinskii-Moriya interaction determines spiral rotation sense.

FeAu₂/Ru(0001) exhibits high magnetic anisotropy energy.

Abstract

We have used ab initio density functional theory to compute the magnetic ground states of the surface alloy systems FeAu$_2$/Ru(0001) and MnAu$_2$/Ru(0001). For both systems, we find that the lowest energy magnetic configuration corresponds to a left-rotating spin spiral, in which the sense of rotation is determined by the Dzyaloshinskii-Moriya interaction. These spirals are lower in energy than the ferromagnetic configuration by 3-4 meV per nm$^2$. We also find that FeAu$_2$/Ru(0001) has a significantly high magnetic anisotropy energy, of the order 1 meV per Fe atom. By comparing with the corresponding freestanding alloy monolayers, we find that the presence of the Ru substrate plays a significant role in determining the magnetic properties of the surface alloy systems.