Charge order in LuFe2O4: an unlikely route to ferroelectricity

TL;DR

This study refines the crystal structure of charge-ordered LuFe2O4, revealing non-polar bilayer arrangements that challenge previous ferroelectricity models based on charge order, and highlights strong charge-spin coupling.

Contribution

It provides a detailed crystal structure refinement showing non-polar bilayers, contradicting earlier ferroelectricity hypotheses based on charge order.

Findings

Charge-ordered LuFe2O4 has non-polar bilayer stacking.

Strong charge-spin coupling is evidenced by x-ray magnetic circular dichroism.

Charge order does not support ferroelectricity in LuFe2O4.

Abstract

We present the refinement of the crystal structure of charge-ordered LuFe2O4, based on single-crystal x-ray diffraction data. The arrangement of the different Fe-valence states, determined with bond-valence-sum analysis, corresponds to a stacking of charged Fe bilayers, in contrast to the polar bilayers previously suggested. This arrangement is supported by an analysis of x-ray magnetic circular dichroism spectra, which also evidences a strong charge-spin coupling. The non-polar bilayers are inconsistent with charge order based ferroelectricity.