Charge and orbital order in Fe_3O_4

TL;DR

This paper investigates charge and orbital ordering in magnetite (Fe_3O_4) at low temperatures using LSDA+U, revealing charge order with a [001] modulation and orbital order consistent with Kugel-Khomskii theory.

Contribution

It provides detailed computational analysis of charge and orbital order in Fe_3O_4, highlighting the effective screening and specific ordering patterns.

Findings

Charge order with [001] modulation identified

Orbital order consistent with Kugel-Khomskii theory

Screening reduces total 3d charge disproportion

Abstract

Charge and orbital ordering in the low-temperature monoclinic structure of magnetite (Fe_3O_4) is investigated using LSDA+U. While the difference between t_{2g} minority occupancies of Fe^{2+}_B and Fe^{3+}_B cations is large and gives direct evidence for charge ordering, the screening is so effective that the total 3d charge disproportion is rather small. The charge order has a pronounced [001] modulation, which is incompatible with the Anderson criterion. The orbital order agrees with the Kugel-Khomskii theory.