Infrared absorption study of charge ordered La0.5Ca0.5−xSrxMnO3(0.1≤x≤0.5)(0.1≤x≤0.5) manganites

Infrared absorption study has been carried out on a series of half doped manganites, La0.5Ca0.5−x SrxMnO3(0.1≤x≤0.5)(0.1≤x≤0.5), with varying magnetic ground state. The charge ordering transition observed in samples with x≤0.3x≤0.3 is accompanied by a mode at ∼525cm−1 in addition to the stretching mode at 615 cm−1 and bending mode at 400 cm−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 727 to 615 cm−1.

Research highlights
► Half doped Manganites.
► Coupling modes of vibration with magnetic ordering.
► Reduction of optical gap with increase in electron bandwidth.