Infrared absorption study of charge ordered $La{}_{0.5}Ca{}_{0.5-x}Sr_{x}MnO_{3}$ $(0.1\leq x\leq0.5$

TL;DR

This study investigates how infrared absorption reveals charge ordering and phonon behavior in La0.5Ca0.5-xSrxMnO3 manganites with different Sr doping levels, showing changes in phonon modes and insulating gap.

Contribution

It provides new insights into the infrared spectral features and charge ordering phenomena in half-doped manganites with varying Sr content.

Findings

Charge ordering mode at ~525cm^{-1} appears for x ≤ 0.3.

Phonon hardening occurs below the antiferromagnetic transition.

Insulating gap decreases from 727cm^{-1} to 615cm^{-1} with Sr doping.

Abstract

Infrared absorption study has been carried out on a series of half doped manganites, $La_{0.5}Ca_{0.5-x}Sr_{x}MnO_{3}$ $(0.1\leq x\leq0.5)$, with varying magnetic ground state. The charge ordering transition observed in samples with {\normalsize $x\leq0.3$ is accompanied by a mode at $\sim525cm^{-1}$ in addition to the stretching mode at $615cm^{-1}$ and bending mode at $400cm^{-1}$. Phonon hardening is found to occur below the CE - type antiferromagnetic ordering temperature. The value of the insulating gap decreases on doping with Sr from $727cm^{-1}$ to $615cm^{-1}.$}