Synthesis and characterization of multiferroic BiMn$_7$O$_{12}$

TL;DR

This paper reports the synthesis and detailed characterization of BiMn$_7$O$_{12}$, a novel multiferroic material with both ferroelectric and antiferromagnetic properties, achieved through high-pressure synthesis and structural analysis.

Contribution

It introduces a new multiferroic compound, BiMn$_7$O$_{12}$, with a unique quadruple perovskite structure exhibiting both ferroelectricity and magnetism.

Findings

BiMn$_7$O$_{12}$ has a non-centrosymmetric structure with a permanent electric dipole.

The compound shows antiferromagnetic transitions similar to related compounds.

Structural analysis reveals a distorted coordination around Bi due to lone pair effects.

Abstract

We report on the high pressure synthesis of BiMn$_7$O$_{12}$, a manganite displaying a "quadruple perovskite" structure. Structural characterization of single crystal samples shows a distorted and asymmetrical coordination around the Bi atom, due to presence of the $6s^{2}$ lone pair, resulting in non-centrosymmetric space group Im, leading to a permanent electrical dipole moment and ferroelectric properties. On the other hand, magnetic characterization reveals antiferromagnetic transitions, in agreement with the isostructural compounds, thus evidencing two intrinsic properties that make BiMn$_7$O$_{12}$ a promising multiferroic material.