Origin of Diffuse Scattering in Relaxor Ferroelectrics

TL;DR

This study combines high-pressure X-ray experiments and molecular dynamics simulations to investigate the origin of diffuse scattering in relaxor ferroelectrics, revealing polarization correlations in chemically-ordered regions as the source.

Contribution

It provides a detailed explanation of diffuse scattering origins in relaxor ferroelectrics through combined experimental and simulation approaches, highlighting the role of polarization correlations.

Findings

Diffuse scattering features are pressure and temperature dependent.

Simulations reproduce experimental diffuse scattering patterns.

Polarization correlations in chemically-ordered regions cause diffuse scattering.

Abstract

High-pressure and variable temperature single crystal synchrotron X-ray measurements combined with first-principles based molecular dynamics simulations study diffuse scattering in the relaxor ferroelectric system PSN (PbSc$_{1/2}$Nb$_{1/2}$O$_3$). Constant temperature experiments show pressure induced transition to the relaxor phase at different temperatures characterized by butterfly and rod shaped diffuse scattering around the $\{$h00$\}$ and $\{$hh0$\}$ Bragg spots, respectively. The simulations reproduce the observed diffuse scattering features as well as their pressure-temperature behavior, and show that they arise from polarization correlations between chemically-ordered regions, which in previous simulations were shown to behave as polar nanoregions. Simulations also exhibit radial diffuse scattering (elongated towards and away from {\bf Q}=(000)), that persists even in the paraelectric phase, consistent with previous neutron experiments on (PbMg$_{1/3}$Nb$_{2/3}$O$_3$) (PMN)