Observation of persistent centrosymmetricity in the hexagonal manganite family

Abstract

The controversy regarding the ferroelectric behavior of hexagonal InMnO${}_3$ is resolved by using a combination of x-ray diffraction (XRD), piezoresponse force microscopy (PFM), second harmonic generation (SHG), and density functional theory (DFT). While XRD data show a symmetry-lowering unit-cell tripling, which is also found in the multiferroic hexagonal manganites of $P{6}_{3}cm$ symmetry, PFM and SHG do not detect ferroelectricity at ambient or low temperature, in striking contrast to the behavior in the multiferroic counterparts. We propose instead a centrosymmetric $P\bar{3}c$ phase as the ground state structure. Our DFT calculations reveal that the relative energy of the ferroelectric and nonferroelectric structures is determined by a competition between electrostatics and oxygen-$R$-site covalency, with an absence of covalency favoring the ferroelectric phase.

8 pages, 9 figures

References in corpus (2)

• Anisotropic conductance at improper ferroelectric domain walls
• Spin-phonon coupling effects in transition-metal perovskites:a DFT+$U$ and hybrid-functional study

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