Correlation between magnetic and transport properties of rare earth doped perovskite manganites La0.6R0.1Ca0.3MnO3 (R = La, Nd, Sm, Gd, and Dy) synthesized by Pechini process

Here, we report a comparative study of rare earth doped La0.6R0.1Ca0.3MnO3 (R = La, Nd, Sm, Gd, and Dy) samples synthesized by sol-gel Pechini process. All the compounds are single-phased and crystallize in Pbnm space group with orthorhombic symmetry. Temperature dependent magnetization measurements revealed that all our compounds exhibit a paramagnetic (PM)-ferromagnetic (FM) transition with decrease in both ordering temperature T-C and the freezing temperature T-F with decrease in ionic radii of lanthanide ions. The compounds display metal-semiconductor transition and the temperatures (T-MS) obtained from the electrical resistivity measurements are consistently higher than those of the Curie temperatures T-C. The transport properties are dominated by the Variable-range hopping (VRH) model above T-MS, showing an increase in characteristic VRH temperature with decreasing size of rare-earth ion. The estimated hopping distance (R-H) in all the samples is close to nearest neighbor Mn-O-Mn distance (similar to 5 angstrom) in the ab plane.