Intrinsic and extrinsic transport properties of Pr 0.67Ba 0.33MnO 3:Ag 2O composites

Abstract

We have studied the electrical resistivity, magnetoresistance (MR), and specific heat of (1 − x) Pr 0.67Ba 0.33MnO 3: xAg 2O ( x = 0–30 mol% Ag 2O) composite manganites. Two insulator–metal-like transitions ( T P1 ∼ 194 K and T P2 ∼ 160 K) are observed in the electrical resistivity behaviour of the pristine material Pr 0.67Ba 0.33Mn O3 (PBMO). With Ag 2O addition, T P1 becomes sharper whereas T P2 disappears beyond 25 mol% Ag 2O addition. Electrical resistivity also decreases in the composites in the whole temperature range of measurement. Intrinsic MR (due to grain) gets enhanced from 22% for the pure sample to ∼40% for 30% Ag 2O sample with 0.6 T field. Extrinsic MR (due to grain boundary), however, is found to decrease with Ag 2O addition. Peak MR enhances in composite at the same temperature and at low temperature, beyond the peak, it is almost constant in a large temperature window. Anomaly observed in the specific heat ( C P) near the high temperature insulator–metal transition temperature for various samples signifies the onset of magnetic ordering. Also C P vs T trend is similar in all the samples indicating that Ag 2O addition does not produce any magnetic inhomogeneity.