Exceptionally large room-temperature ferroelectric polarization in the novel PbNiO3 multiferroic oxide

TL;DR

This study reveals that PbNiO3 is a proper ferroelectric with an exceptionally large room-temperature polarization exceeding that of BiFeO3, driven by Pb-O displacements and lone-pair hybridization.

Contribution

It demonstrates that PbNiO3 exhibits a record-high polarization driven by Pb-O displacements and hybridization, expanding understanding of multiferroic materials.

Findings

PbNiO3 has a polarization of about 100 μC/cm^2.

The ferroelectricity is driven by Pb-O displacements and lone-pair hybridization.

PbNiO3's polarization exceeds that of BiFeO3.

Abstract

We present a study based on several advanced First-Principles methods, of the recently synthesized PbNiO3 [J. Am. Chem. Soc 133, 16920 (2011)], a rhombohedral antiferromagnetic insulator which crystallizes in the highly distorted R3c crystal structure. We find this compound electrically polarized, with a very large electric polarization of about 100 (\muC/cm)^2, thus even exceeding the polarization of well-known BiFeO3. PbNiO3 is a proper ferroelectric, with polarization driven by large Pb-O polar displacements along the [111] direction. Contrarily to naive expectations, a definite ionic charge of 4+ for Pb ion can not be assigned, and in fact the large Pb 6s-O 2p hybridization drives the ferroelectric distortion through a lone-pair mechanism similar to that of other Pb- and Bi-based multiferroics