The effect of Cu substitution on the A1g mode of La(0.7)Sr(0.3)MnO3 manganites

TL;DR

This study investigates how copper substitution affects the Raman spectra, especially the A1g mode, of La(0.7)Sr(0.3)MnO3 manganites, revealing a linear relationship with structural parameters.

Contribution

It provides the first Raman analysis of Cu-substituted La-Sr-Mn-O manganites and links phonon shifts to structural changes due to Cu doping.

Findings

A1g mode shifts linearly with Cu substitution

Raman spectra show characteristic peaks at 190-220, 430, 500, and 670 cm-1

Structural parameters influence phonon behavior

Abstract

We report on the first Raman data of Cu substituted La(1-y)Sr(y)Mn(1-x)Cu(x)O3 (0 < x < 0.10 and 0.17 < y < 0.3, accordingly in order to have the same Mn(4+)/[Mn(4+)+Mn(3+)] ratio), collected in the frequency range 100-900 cm-1 and at room temperature, with parallel and crossed polarizations of the incident and scattered light. Spectra were fitted with a Drude-Lorentz model, and peaks at 190-220 and 430 cm-1, together with two broad structures centered at near 500 and 670 cm-1, have been found. We also have observed that the A1g mode is substantially shifted with increasing Cu substitution. The A1g phonon shift is a linear function of the tolerance factor t and the rhombohedral angle, thus following the structural changes of the MnO6 octahedra in the system.