Multiferroic FeTe$_2$O$_5$Br: Alternating spin chains with frustrated interchain interactions

TL;DR

This study reveals that multiferroic FeTe₂O₅Br consists of alternating antiferromagnetic chains with frustrated interchain interactions, and explains its temperature-dependent magnetic behavior and electric polarization through interchain exchange effects.

Contribution

It redefines the magnetic structure of FeTe₂O₅Br from tetramer models to alternating chains with frustrated interactions, supported by combined theoretical and experimental analysis.

Findings

FeTe₂O₅Br is composed of alternating antiferromagnetic chains.

Frustrated interchain interactions influence magnetic and electric properties.

Temperature dependence of magnetic vector explained by exchange striction.

Abstract

A combination of density functional theory calculations, many-body model considerations, magnetization and electron spin resonance measurements shows that the multiferroic FeTe$_2$O$_5$Br should be described as a system of alternating antiferromagnetic $S=5/2$ chains with strong Fe-O-Te-O-Fe bridges weakly coupled by two-dimensional frustrated interactions, rather than the previously reported tetramer models. The peculiar temperature dependence of the incommensurate magnetic vector can be explained in terms of interchain exchange striction being responsible for the emergent net electric polarization.