Frustrated magnetism in Mn films on Ag(111) surface: from chiral in-plane N\'eel state to row-wise antiferromagnetism

TL;DR

This study uses advanced DFT methods to reveal that Mn monolayers on Ag(111) exhibit a chiral Neel magnetic state at low temperatures, with a potential transition to row-wise antiferromagnetism at higher temperatures, resolving longstanding experimental-theoretical discrepancies.

Contribution

The paper demonstrates that the ground state of Mn/Ag(111) is a chiral Neel state, challenging previous predictions of collinear RW-AFM, and shows temperature-dependent magnetic phase stability.

Findings

Chiral Neel state is the ground state at low temperatures.

Disordered local moment approach indicates possible stabilization of RW-AFM at higher temperatures.

The study resolves a long-standing controversy between experimental observations and theoretical predictions.

Abstract

We conduct a comprehensive density functional theory (DFT) study to explore the intricate magnetic properties of frustrated Mn monolayer on the Ag(111) surface. Spin-polarized scanning tunneling microscopy demonstrates that a N\'eel magnetic state characterizes such an interface, which contradicts systematic ab-initio predictions made in the last two decades indicating that the ground state is collinear row-wise antiferromagnetic (RW-AFM) state. Here, we employ the all-electron full-potential Korringa-Kohn-Rostoker Green function (KKR) method and find that the ground state is a chiral magnetic N\'eel state, with magnetic moments rotating in the surface plane following a unique sense of rotation, as dictated by the underlying in-plane magnetic anisotropy and Dzyaloshinskii-Moriya interaction. Once allowing disordered magnetic states, as described within the disordered local moment (DLM) approach, we reveal the possibility of stabilization of a RW-AFM state. We conjecture that at low temperatures, the chiral N\'eel state prevails, while at higher temperatures, the magnetic exchange interactions are modified by magnetic disorder, which can then induce a transition towards a RW-AFM state. Our work addresses a long term experimental-theoretical controversy and provides significant insights into the magnetic interactions and stability of Mn films on noble metal substrates, contributing to the broader understanding of the different magnetic facets of frustrated magnetism in thin films.