Inter Comparison of the Magneto Transport of La$_{2/3}$Ca$_{1/3}$MnO $_{3}$:Ag/In Polycrystalline Composites

In this paper, we report the synthesis, magnetotransport features, and magnetization of polycrystalline La
_2/3
Ca
_1/3
MnO
₃
:Ag
_x
/Inx composites with x=0,0.1,0.2,0.3 and 0.4. In the case of La
_2/3
Ca
_1/3
MnO
₃
: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
_2/3
Ca
_1/3
MnO
₃
:Ag
_x
composites is explained on the basis of improved grains size. Interestingly the La
_2/3
Ca
_1/3
MnO
₃
: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