Inter Comparison of the Magneto Transport of La $_{2/3}$ Ca $_{1/3}$ MnO

In this paper, we report the synthesis, magnetotransport features, and magnetization of polycrystalline La_2/3Ca_1/3MnO ₃:Ag_x/Inx composites with x=0,0.1,0.2,0.3 and 0.4. In the case of La_2/3Ca_1/3MnO₃:Ag_x , the temperature coefficient of resistance (TCR) near ferromagnetic (FM) transition enhances significantly with the addition of Ag. The FM transition temperature (T^FM) is also increased slightly with Ag doping. Magnetotransport measurements revealed that magnetoresistance (MR) is found to be maximum near T^FM. Very sharp TCR is seen near T^FM with the highest value of up to 15 % for an Ag (0.4) sample, which is an order of magnitude higher than for pristine sample and is the best value yet reported for any polycrystalline LCMO compound. Increased TCR, T^FM, and significant above room temperature MR of La_2/3Ca_1/3MnO₃:Ag_x composites is explained on the basis of improved grains size. Interestingly the La_2/3Ca_1/3MnO₃:In_x composites behaved exactly in the opposite way, resulting in decreased T ^FM, and TCR compared to the pristine LCMO compound. In fact, the grains morphology of LCMO:In_x composites is seen to be inferior to pristine LCMO which is opposite of the LCMO:Ag_x case