Preparation of some nano size colossal magneto resistance materials by the sol-gel route

Abstract

A series of colossal magneto resistance materials having compositional formula Re_0.67Sr_0.33MnO₃ (Re=Nd, Gd,...etc.) were prepared by the sol-gel method, using Ethylene glycol as a gelating reagent. The materials were characterized by the powder X-ray diffraction technique and are found to be single phase with orthorhombic structure. The particle size of all the materials were calculated using the well known Shearer formula and are found to be in the range of 20-45 nm. In order to determine the transition temperature (T_c), the DC electrical resistivity measurements were also carried out over a temperature range 80-300 K using the four probe method and it has been observed that the T_c values are found to increase with increasing ionic size. Finally the magneto resistance measurements were also undertaken in the temperature range 80-300 K and it has been found that the MR values of these materials are better when compared with those prepared by the solid state reaction method.