Role of Te in the low dimensional multiferroic material FeTe2O5Br

TL;DR

This study uses first-principles calculations to explore how Te ions influence the magnetoelectric effect in the low-dimensional multiferroic FeTe2O5Br, highlighting the role of exchange striction and Te ions in electric polarization.

Contribution

It reveals the specific role of Te^4+ ions in inter-tetramer exchange and polarization, advancing understanding of multiferroic mechanisms in FeTe2O5Br.

Findings

Te ions contribute to electric polarization after magnetic ordering

Exchange striction drives the magnetoelectric effect

Te lone pairs are antipolar and do not induce polarization without magnetism

Abstract

Using first principles density functional calculations, we study the electronic structure of the low-dimensional multiferroic compound FeTe2O5Br to investigate the origin of the magnetoelectric (ME) effect and the role of Te ions in this system. We find that without magnetism even in the presence of Te-5s lone pairs, the system remains centrosymmetric due to the antipolar orientation of the lone pairs. Our study shows that the exchange striction within the Fe tetramers as well as between them is responsible for the ME effect in FeTe2O5Br. We also find that the Te^4+ ions play an important role in the inter-tetramer exchange striction as well as contribute to the electric polarization in FeTe2O5Br, once the polarization is triggered by the magnetic ordering.