Transport properties of Cs doped Pr2/3(Ba1-xCsx)1/3MnO3 manganites

Magneto-transport behaviour of Pr2/3Ba1/3MnO3 manganite (PBMO) doped with Cs at Ba-site is reported here. The observed decrease in the Curie temperature TC and the two insulator-metal like transitions (at TP1 and TP2) in PBMO with Cs doping have been discussed in the light of the decrease in the carrier concentration emanating due to the change in the Mn3+/Mn4+ ratio. While the peak magnetoresistance (MR) value at TP1 (reminiscent of the intra-granular behaviour) remains nearly invariant, the inter-granular (grain boundary) behaviour is clearly reflected through a substantial higher value of MR below TP2. The insulating behaviour above TP1 has been co-related to the decrease in the density of states at the Fermi level and is substantiated by the observed decrease in the resistivity with magnetic field. Electron-magnon scattering process has been invoked to consider the ferromagnetic metallic state below TP2