Magnetotransport in La0.7Ca0.3MnO3-PMMA composites synthesized by polymeric precursor route

A detailed investigation on the effect of PMMA on the structure, microstructure and magnetotransport properties of manganite La0.7Ca0.3MnO3 (LCMO) is presented. LCMO-PMMA nano-composites have been synthesized by a unique polymeric sol-gel route, which leads to improved solubility of PMMA in the LCMO matrix. The LCMO phase is grown in the presence of varying PMMA concentration at ∼500 °C. This route yields single-phase material at significant lower temperature (∼500 °C) and the grain size is observed to decrease slightly with increasing PMMA concentration. On increasing the PMMA concentration, TC undergoes a small decrease, resistivity is observed to increase by two orders of magnitude, with a concomitant large decrease in TIM, e.g., from ∼218 K for virgin LCMO to ∼108 K for ∼50 wt% PMMA admixed LCMO. Low field magnetoresistance measured in the temperature range 77-300 K shows considerable enhancement as a function of the PMMA concentration. These phenomena are explained by taking into account the increased intergranular disorder as a consequence of PMMA admixture.