Distinct insulating state below the curie point in Pr{sub 0.7}Ba{sub 0.3}MnO{sub 3}

Magnetization, resistivity, thermal expansion, thermopower, and neutron powder diffraction data are presented for the perovskite manganite Pr{sub 0.7}Ba{sub 0.3}MnO{sub 3}. A distinct ferromagnetic insulating state, similar to that observed in the La{sub 0.88}Sr{sub 0.12}MnO{sub 3} system, is observed in the temperature range between the paramagnetic-ferromagnetic transition at TFM{approx}180 K and the broad metal-insulator transition near T{sub p}=120 K. The large A-site cation-size mismatch appears to suppress the ferromagnetic double-exchange interactions relative to the competing ferromagnetic superexchange interactions, thereby giving rise to the ferromagnetic insulating state.