Cr-doping effect on the structural, magnetic, transport properties and Raman spectroscopy of La(2+x)/3Sr(1-x)/3Mn1-xCrxO3 perovskites

A series of the double-doping samples La(2+x)/3Sr(1-4x)/3Mn1-xCrxO3 (0 <= x <= 0.25) with the Mn3+/Mn4+ ratio fixed at 2:1 have been fabricated. The structural, magnetic, transport properties and Raman spectroscopy have been investigated, and no apparent crystal structure change is introduced by Cr doping up to x = 0.25. But the Curie temperature T-C and metal-insulator transition temperature T-MI are strongly affected by Cr substitution. The room temperature Raman spectra start exhibiting some new features following the increasing concentration of Cr substitutions. Moreover, it is worth noting that the frequency of the A(1g) phonon mode can also be well correlated with the A-site mismatch effect (sigma(2)), which is influenced mainly by the variety of the Sr content. (C) 2007 Elsevier Ltd. All rights reserved.