Magnetoresistance and magnetocaloric properties of Pr0.68Ca0.32-xBixMn03 (x= 0, 0.1, 0.18, 0.26 and 0.32) compounds

The structural, magnetic and magnetocaloric properties of the polycrystalline Pr0.68Ca0.32−xBixMnO3 (x = 0, 0.1, 0.18, 0.26 and 0.32) samples were studied. X-ray analyses indicated that all samples have a single phase of orthorhombic symmetry. The charge-order transition was observed for the x = 0 sample at TCO = 200 K, and it disappears with further Bi doping of the sample. The Curie temperature, saturation magnetisation and magnetocaloric effect decrease with increasing Bi content. The decrease in Curie temperature and saturation magnetisation was attributed to magnetic inhomogeneity and weakening of double-exchange interaction in the Bi-doped samples. The decrease in mannetic entropy change with increasing Bi content was attributed to decrease in saturation magnetisatio and the nature of phase transition transformed from first order to second order with increasing Bi content. The metal-insulating phase transition of the material clearly seen from R-T curves. % MR was obserwed to decrease with increasing Bi content.