Structure and magnetism of the $(2 \times 2)$-FeO(111) surface

TL;DR

This study uses ab initio calculations to analyze the structure and magnetic properties of the $(2 imes 2)$-FeO(111) surface, revealing coexistence of different environments and the influence of substrate effects.

Contribution

It provides a detailed theoretical analysis of the FeO(111) surface reconstruction, highlighting the coexistence of wurtzite and spinel-like environments and their impact on surface magnetism.

Findings

Both wurtzite and spinel-like environments are possible.

Surface phase diagram shows competition of charge and magnetic effects.

Net surface magnetization arises from frustration and exchange interactions.

Abstract

Based on ab initio calculations we determine the features and relative stability of different models proposed to describe the $(2 \times 2)$-FeO(111) reconstruction. Our results suggest that both wurtzite and spinel-like environments are possible, and their coexistence explains phenomena of biphase ordering. The surface phase diagram reflects a competition of charge and magnetic compensation effects, and reveals the important influence of the substrate on the final surface structure. Though antiferromagnetic couplings are dominant, frustration and the delicate balance of surface and bulk exchange interactions lead to a net surface magnetization that accounts for the large measured values.