Large magnetocaloric effect above 300 K and magnetoresistance pine r(oLvas k0i.t5ePsr0.5)1-xPbxMnO3 perovskites

Abstract

Perovskite compounds (La0.5Pr0.5) 1-xPbxMnO3 (x = 0.1 - 0.5) with orthorhombic structure were prepared by using a solid-state reaction technique. In the studied samples, the spin-glass-like state occurs at low temperatures and the Curie temperature, Tc, increases from 170 K (x = 0.1) to 336 K (x = 0.5) because of a strong double exchange. The magnetic entropy change, |??Sm|, reached its largest value of 2.06 J/kg?K at ??H = 13.5 kOe for the sample with x = 0.4 (Tc = 323 K). Due to the large |??Sm| and high Tc, these materials are suggested for use as active magnetic refrigerants for magnetic refrigeration technology at temperatures above room temperature. While the conductivity of the samples with x = 0.1 and 0.2 exhibits only a semiconducting behavior over the whole measured temperature range, there is insulator-metallic phase transition on the R(T) curves of the samples with x = 0.3 - 0.5. The magnetoresistance of the samples was measured and large values for MR were found.