Improper ferroelectricity and multiferroism in 2HBaMnO$_3$

TL;DR

This study predicts that 2H-BaMnO3 undergoes an improper ferroelectric phase transition to a multiferroic state with antiferromagnetic properties, based on first-principles calculations.

Contribution

It is the first theoretical prediction of improper ferroelectricity and multiferroism in 2H-BaMnO3 using first-principles methods.

Findings

Predicted phase transition from P63/mmc to P63cm structure.

2H-BaMnO3 is expected to be multiferroic at low temperature.

Transition mechanism similar to YMnO3 despite different atomic arrangements.

Abstract

Using first-principles calculations, we study theoretically the stable 2H hexagonal structure of BaMnO3. We show that from the stable high temperature P63/mmc structure, the compound should exhibit an improper ferroelectric structural phase transition to a P63cm ground state. Combined with its antiferromagnetic properties, 2H-BaMnO3 is therefore expected to be multiferroic at low temperature. The phase transition mechanism in BaMnO3 appears similar to what was reported in YMnO3 in spite of totally different atomic arrangement, cation sizes and Mn valence state.