Polaron population controlled of modulation wave vector Manganites

TL;DR

This study investigates charge ordering in calcium-doped lanthanum manganites using TEM, revealing temperature-dependent incommensurate charge order and a linear relationship between superlattice intensity and modulation wave vector.

Contribution

It demonstrates the role of Coulomb interactions in polaron population and charge order formation in manganites, providing new insights into their charge ordering mechanisms.

Findings

Diffuse charge ordering persists at room temperature.

Superlattice intensity and wave vector increase with decreasing temperature.

Linear relationship between superlattice intensity and modulation wave vector.

Abstract

The growth of charge ordering phenomenon in calcium doped lanthanum manganites La1-xCaxMnO3, x 0.62, 0.67 has been studied using transmission electron microscopy TEM. The diffuse intensity characteristic of short range charge ordering is observed even at room temperature. This diffuse intensity has the local intensity maxima at the incommensurate positions q. With decreasing temperature, the intensity I of super lattice charge ordered spot and the magnitude of its modulation wave vector q increases and there exists a linear relationship between I and q of super lattice charge ordered spot. This linear dependence can be explained taking in to account the population and the columbic interactions between the correlated polarons. It appears that the columbic interactions between the correlated polarons lead to the coherent distributions of eg charge carriers and thereby giving rise to the uniformly periodic superlattice charge ordered state to these manganites.