Low field magnetoresistance, temperature coefficient of resistance and magnetocaloric effect in Pr_(2/3)Ba_(1/3)MnO_3:PdO composites

摘要

Electrical resistivity, magnetoresistance (MR), temperature coefficient of resistance (TCR) and magnetocaloric effect of (1-x) Pr_(2/3)Ba_(1/3)MnO_3:x PdO (x = 0-30 mol% PdO) composite manganites are reported here. Pristine sample Pr_(2/3)Ba_(1/3)MnO_3 (PBMO) shows two insulator-metal like transitions (T_(P1)～194K and T_(p2)～160K) in the electrical resistivity behavior. With PdO, T_(P1) becomes sharper whereas T_(P2) disappears beyond 10 mol% PdO addition. The intrinsic MR gets enhanced from 22% for the pristine sample to ～42% for 27% PdO sample. However, the extrinsic MR is found to decrease in the composites. The TCR also increases from a negligible value for PBMO to 8% for 25 mol% PdO sample. These features have been explained on the basis of opening of new conducting channels and decrease in spin dependent scattering and the overall decrease in electrical resistivity. The magnetic entropy change and relative cooling power (RCP) for the PBMO sample are 5.3418J.Kg-K and 304.5428 J/Kg respectively. However, these values decrease in the composites.