New phase transition in $Pr_{1-x}Ca_xMnO_3$ system: evidence for electrical polarization in charge ordered manganites

TL;DR

This study reveals a new phase transition in Pr_{1-x}Ca_xMnO_3 manganites, characterized by electric field gradient changes indicating spontaneous local electric polarization within the charge ordered phase.

Contribution

It provides experimental evidence for a previously unreported phase transition associated with electric polarization in charge-ordered manganites.

Findings

Distinct EFG behaviors inside and outside the charge order region

Identification of a discontinuous phase transition between charge ordering and Neel temperatures

Evidence of spontaneous local electric polarization below the charge order transition

Abstract

A detailed study of the electric field gradient (EFG) across the Pr1-xCaxMnO3 phase diagram and its temperature dependence is given. Clearly, distinct EFG behaviours for samples outside/inside the charge order (CO) region are observed. The EFG temperature dependence evidences a new phase transition occurring over the broad CO region of the phase diagram. This transition is discontinuous and occurs at temperatures between the charge ordering and the Neel temperatures. The features observed in the EFG are associated with polar atomic vibrations which eventually lead to a spontaneous local electric polarization below CO transition.