Effect of hydrostatic pressure on the resistivity of La$_{0.8}$Ag$_{0.1}$MnO$_3$ ceramic near $T_C$

The effect of hydrostatic pressure up to $8.5$ GPa on the transport characteristics of granular ceramic manganite La$_{0.8}$Ag$_{0.1}$MnO$_3$ near the temperature corresponding to the magnetoresistance peak has been studied. The electrical resistivity has been measured in the temperature range of $275$–$320$ K at pressures $P = 0, 0.44, 2.32, 3.81$, and $4.84$ GPa. The temperature of the transition from the metallic to semiconductor type of conductivity is a monotonically increasing function of the applied pressure with a slope of $4.54$ K/GPa. At $296$ K, the linear logarithmic plot of the pressure dependence of the resistivity exhibits an anomaly in the form of a kink at $3.85$ GPa. It has been shown that the observed transition with a change in the slope in the logarithmic plot of the pressure dependence of the resistivity is due to the existence of two scattering processes: intragranular and near-boundary ones. Near the transition point, both scattering processes make comparable contributions to the resistivity. For pressures $P < 3.85$ GPa, the contribution to the resistivity from scattering in the boundary layers of grains dominates, whereas the contribution from the homogeneous material within the grains is dominant in the high-pressure range.