Transport Properties of Transitional Metal (Ni2+) Doped La0.67Ca0.33MnO3 Rare-Earth Manganites.

The crystalline samples of La0.67Ca0.33Mn1-xNixO3 (x = 0, 0.05, and 0.1) manganites were prepared by conventional solid-state reaction method. The analysis of X-ray diffraction spectra revealed that all the prepared samples are single phased in nature and have acquired orthorhombic structure with space group Pbnm. Temperature-dependent dc resistivity measurements infer metallic nature of the samples in the lower temperature region (T > 50 K) where metal to insulator transition (TMI) occurs at temperature 238 K, 204 K, and 187 K for x = 0, 0.05, and 0.1, respectively. For the temperature below 50 K, a kind of transition from paramagnetic insulator to the ferromagnetic metallic phase was observed in all the materials. The application of magnetic field of 8 T indicates the shift of TMI toward the higher temperature region with high reduction in resistivity due to suppression of any thermal agitations present. The resistivity data analysis for conduction mechanism above 50 K infers that the grain/domain boundary scattering processes play a dominant role in the the metallic region. However, the analysis of the region below 50 K infers that weak localization effect is the responsible factor in conduction phenomena. Isothermal at 300 K for magnetoresistance study conveys that the pristine La0.67Ca0.33MnO3 manganite exhibits larger MR effect with rise in magnetic field compared to doped ones. [ABSTRACT FROM AUTHOR]