Phenomenological Landau analysis of predicted magnetoelectric fluorides: KMnFeF$_{6}$ and Ba$_{2}$Ni$_{7}$F$_{18}$

TL;DR

This paper uses Landau theory and symmetry analysis to study the magnetoelectric properties of predicted multiferroic fluorides KMnFeF$_{6}$ and Ba$_{2}$Ni$_{7}$F$_{18}$, revealing additional polarization effects below magnetic transition temperatures.

Contribution

It provides a phenomenological Landau analysis of magnetoelectric effects in specific fluorides, highlighting the emergence of additional polarization independent of the linear magnetoelectric effect.

Findings

Additional electrical polarization appears below magnetic ordering temperature.

The magnitude of this polarization depends on dielectric susceptibility.

The study demonstrates the generality of this phenomenon in magnetoferroelectrics.

Abstract

Recently, we predicted based on symmetry considerations that KMnFeF$_{6}$ and Ba$_{2}$Ni$_{7}$F$_{18}$ are likely magnetoelectric multiferroic materials. In this contribution, we investigate with Landau theory and crystal structure considerations the polarization and the linear magnetoelectric effect in these materials. Based on these two examples, we show that any magnetoferroelectric will display additional electrical polarization below its magnetic ordering temperature. This additional electrical polarization is not related to the linear magnetoelectric effect. Its magnitude depends on the dielectric susceptibility.