BaFe$_2$Se$_3$: a high $T_{\rm C}$ magnetic multiferroic with large ferrielectric polarization

TL;DR

BaFe$_2$Se$_3$ is predicted to be a high-temperature magnetic multiferroic with significant ferrielectric polarization driven by magnetic order, offering potential for multifunctional applications.

Contribution

This work predicts a novel ferrielectric multiferroic state in BaFe$_2$Se$_3$, driven by exchange striction, with large polarization and high transition temperature, distinct from typical multiferroics.

Findings

BaFe$_2$Se$_3$ exhibits ferrielectric polarization of ~0.1 μC/cm².

A fully ferroelectric state has an even larger polarization (~2-3 μC/cm²).

The material is predicted to have a high Curie temperature.

Abstract

The iron-selenides are important because of their superconducting properties. Here, an unexpected phenomenon is predicted to occur in an iron-selenide compound with a quasi-one-dimensional ladder geometry: BaFe$_2$Se$_3$ should be a magnetic ferrielectric system, driven by its magnetic block order via exchange striction. A robust performance (high $T_{\rm C}$ and large polarization) is expected. Different from most multiferroics, BaFe$_2$Se$_3$ is ferrielectric, with a polarization that mostly cancels between ladders. However, its strong magnetostriction still produces a net polarization that is large ($\sim$$0.1$ $\mu$C/cm$^2$) as compared with most magnetic multiferroics. Its fully ferroelectric state, with energy only slightly higher than the ferrielectric, has a giant improper polarization $\sim$$2-3$ $\mu$C/cm$^2$.