Effect of Re doping on structure and magneto-electrical properties of La1.2Re0.2Ca1.6Mn2O7 manganites
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In this paper, the structural and magneto-electrical properties of the double layered La12Re0.2Ca1.6Mn2O7 manganites doped with Re=La, Pr, Eu, Y and Gd are presented. The results show that the decreasing of the ionic radii of the doping element decreases the lattice parameters. The grain size of the samples also decreases in the same order. Except for Pr, the doping decreases the metal-insulator transition temperature (T-MI) and increases the resistivity. The doped samples exhibit higher magnetoresistance (MR) than the undoped one on a large domain of temperature. The highest value is seen for the Eu doped sample and is about 91.96% at 139.4 K and 5 T. This sample exhibits a crossover from positive to negative MR for temperatures greater than T-MI. The obtained minimum of MR is about - 100.7% at 185.4 K. (C) 2013 Elsevier B.V. All rights reserved.