Abstract
With an aspect to understand the influence of cation mismatch on magneto-transport properties of colossal magnetoresistive (CMR) materials, a systematic study of La0.65Ca0.35-xLixMnO3 (0 ≤ x ≤ 0.15) manganites has been undertaken. The materials were synthesized by sol-gel Pechini process and their structures were confirmed by the analysis of XRD data using Rietveld refinement technique. A paramagnetic to ferromagnetic transition and a semiconductor to metallic one have been observed at low temperature. Both Curie temperature (Tc) and metal-semiconductor transition temperature (TMS) in the vicinity of Tc first increases with Li doping and then show a decreasing trend, which is justified on the basis of a competition between double-exchange and super-exchange mechanisms. It has been concluded that the electrical resistivity data in high-temperature paramagnetic-semiconducting region (T > TMS) may be described by the small polaron hopping model. Also, a large magnetoresistance (MR%) has been observed in the vicinity of metal-semiconductor transition temperature TMS, which is comparable to the MR% in the low-temperature region.
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