Evidence of magnetic polaronic states inLa0.70Sr0.30Mn1−xFexO3manganites

Abstract

We have performed x-ray, electrical resistivity, and Raman scattering measurements in ${\mathrm{La}}_{0.70}{\mathrm{Sr}}_{0.30}{\mathrm{Mn}}_{1\ensuremath{-}x}{\mathrm{Fe}}_{x}{\mathrm{O}}_{3}$ manganites, with x varying from 0 to 0.40. The appearance of new peaks in the Raman spectra as the Fe content increases is attributed to either otherwise forbidden Raman modes that become active due to symmetry breaking effect or to the phonon density of states features, which arise due to a disorder-induced phenomenon. The softening of some phonon modes suggests the evidence of magnetic polaronic states in the insulating paramagnetic phase of these manganites. Our observations are discussed in connection with the x-ray diffraction and electrical resistivity data.