Is hexagonal InMnO3 ferroelectric?

TL;DR

This study confirms that hexagonal InMnO3 is ferroelectric at low temperatures with a specific symmetry, exhibiting topological vortex domains, and identifies a high-temperature non-ferroelectric phase that can be quenched to room temperature.

Contribution

The paper provides comprehensive experimental evidence that h-InMnO3 is ferroelectric at low temperatures and details its domain structure, clarifying the debate on its ferroelectric nature.

Findings

h-InMnO3 is ferroelectric with P6_3cm symmetry at low T

A non-ferroelectric P-3c1 phase exists at high T

Domain vortices are observed in the ferroelectric phase

Abstract

The presence of ferroelectricity in hexagonal (h-)InMnO3 has been highly under debate. The results of our comprehensive experiments of low-temperature (T) polarization, TEM and HAADF-STEM on well-controlled h-InMnO3 reveal that the ground state is ferroelectric with P6_3cm symmetry, but a non-ferroelectric P-3c1 state exists at high T, and can be quenched to room T. We also found that the ferroelectric P6_3cm state of h-InMnO3 exhibits the domain configuration of topological vortices, as has been observed in h-REMnO3 (RE=rare earths).