Microscopic flexoelectricity in the canonical PMN relaxor

TL;DR

This study revisits neutron scattering data on PMN relaxor ferroelectric to assess intrinsic flexoelectricity, finding its magnitude similar to conventional ferroelectrics and suggesting relaxor behavior relates to suppressed correlation lengths near a Lifshitz point.

Contribution

It provides the first direct estimate of the flexoelectric coupling coefficient in PMN from neutron data, linking relaxor properties to fluctuation suppression near a Lifshitz point.

Findings

Flexoelectric coupling coefficient in PMN is within typical ferroelectric range.

Relaxor behavior may be due to suppressed correlation lengths of fluctuations.

The findings are explained using Ginzburg-Landau-Devonshire and soft mode theories.

Abstract

Previously reported neutron scattering investigations of the canonical relaxor ferroelectric perovskite oxide with a chemical formula Pb(Mg(1/3)Nb(2/3))O3 (PMN) are revisited in order to appreciate the role of the intrinsic bulk flexoelectricity. Despite the outstanding electromechanical properties of lead-based relaxors, the magnitude of the flexoelectric coupling coefficient derived here directly from the PMN neutron diffuse scattering data, does not exceed the range of values typical for conventional perovskite ferroelectrics. We explain how these findings are related in the framework of the Ginzburg-Landau-Devonshire and the ferroelectric soft mode theory. We propose that the relaxor properties of PMN might be related to the suppression of the transverse correlation length of the flexoelectrically hybridized translational-polarization fluctuations due to its closeness to the Lifshitz-point regime.