Effects of Transition-Metal V-Doping on the Structural, Magnetic and Transport Properties in La0.67Sr0.33MnO3 Manganite Oxide

We have investigated the structural, magnetic, and electrical transport properties of a series of ABO3-type perovskite compounds, La0.67Sr0.33Mn1−xVxO3 (0≤x≤0.15). The samples were characterized by X-ray diffraction and data were analyzed using Rietveld refinement technique, it has been concluded that these materials have the rhombohedral structure with \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$\mathrm{R}\overline{3}\mathrm{C}$\end{document} space group. The magnetization and resistivity measurements versus temperature proved that all our samples exhibit a ferromagnetic to paramagnetic transition and a metallic to semiconductor one when the temperature increases. Both the Curie temperature TC and the resistivity transition temperature TP of the composites decrease, while the resistance increases as the V content increases. It has been concluded that the electrical conduction mechanism in the metallic regime at low temperatures (T<TP) can be explained on the basis of grain boundary effects and the single electron-magnon scattering process. Resistivity data were well fitted with the relation ρ=ρ0+ρ2T2+ρ4.5T4.5, whereas the adiabatic Small Polaron Hopping (SPH) and Variable Range Hopping (VRH) models are found to fit well in the paramagnetic semiconducting regime at the high temperature (T>TP).