Investigation of structural and some physical properties of Cr substituted polycrystalline Eu_(0.5)Sr_(0.5)Mn_(1-x)Cr_xO_3 (0 ≤ x ≤ 0.1) manganites

摘要

The polycrystalline samples with nominal composition Eu_(0.5)Sr_(0.5)Mn_(1-x)Cr_xO_3 (0 ≤ x ≤ 0.1) were prepared by the conventional solid state reaction method and characterized by X-ray diffraction, scanning electron microscopy and electrical resistivity behavior without and with magnetic field. The structural parameters obtained by using Rietveld refinement of X-ray diffraction data showed that all samples crystallize with orthorhombic perovskite type symmetry with Pbnm space group. The scanning electron micrograph images reveal that the increase in Cr substitution hinders grain growth and grain connectivity. The temperature dependence of electrical resistivity show the semiconducting nature of these compounds and support the small polaron hoping model and variable range hopping conduction model. The calculated hopping distance and activation energy decreased as rate of Cr content increased whereas density of states at Fermi level increased. A large negative magnetoresistance is also present in the sample at the lowest temperature of measurements.