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, La_0.67Sr_0.33Mn_1?x V _x O₃ (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 $mathrm{R}overline{3}mathrm{C}$ 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 T _C and the resistivity transition temperature T _P 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<T _P) 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=ρ ₀+ρ ₂ T ²+ρ _4.5 T ^4.5, 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>T _P).