Charge order in Fe2OBO3: An LSDA+U study

TL;DR

This study uses LSDA+U calculations to analyze charge ordering in Fe2OBO3, revealing significant t2g occupancy differences but small total charge separation, and links the charge order to structural and magnetic properties.

Contribution

The paper provides a detailed LSDA+U analysis of charge ordering in Fe2OBO3, connecting electronic structure with magnetic interactions and structural distortions.

Findings

Large t2g occupancy difference indicates charge order

Small total 3d charge separation due to effective screening

Interribbon exchange interactions dominate magnetic structure

Abstract

Charge ordering in the low-temperature monoclinic structure of iron oxoborate (Fe2OBO3) is investigated using the local spin density approximation (LSDA)+U method. While the difference between t_{2g} minority occupancies of Fe^{2+} and Fe^{3+} cations is large and gives direct evidence for charge ordering, the static "screening" is so effective that the total 3d charge separation is rather small. The occupied Fe^{2+} and Fe^{3+} cations are ordered alternately within the chain which is infinite along the a-direction. The charge order obtained by LSDA+U is consistent with observed enlargement of the \beta angle. An analysis of the exchange interaction parameters demonstrates the predominance of the interribbon exchange interactions which determine the whole L-type ferrimagnetic spin structure.