Incipient ferroelectricity in 2.3% tensile-strained CaMnO3 films

TL;DR

This study demonstrates that CaMnO3 films under 2.3% tensile strain exhibit incipient ferroelectricity below 25 K, detected via optical SHG, with polarization aligned along specific crystallographic axes as predicted by calculations.

Contribution

First experimental evidence of incipient ferroelectricity in strained CaMnO3 films using optical SHG and density functional theory predictions.

Findings

Incipient ferroelectricity observed below 25 K.

Polarization aligns with theoretical predictions.

Optical SHG effectively detects incipient polarization.

Abstract

Epitaxial CaMnO3 films grown with 2.3% tensile strain on (001)-oriented LaAlO3 substrates are found to be incipiently ferroelectric below 25 K. Optical second harmonic generation (SHG) was used for the detection of the incipient polarization. The SHG analysis reveals that CaMnO3 crystallites with in-plane orientation of the orthorhombic b axis contribute to an electric polarization oriented along the orthorhombic a (resp.\ c) axis in agreement with the predictions from density functional calculations.