Transport behavior and mechanism of conduction of simultaneously substituted Y and Fe in La0.7Ba0.3MnO3 perovskite

The electrical properties and the mechanism of conduction of the simultaneously substituted La0.7−xYxBa0.3Mn1−xFexO3 perovskite (0≤x≤0.30) have been studied. The insertion of Y3+ and Fe3+ ions in the parent compound La0.7Ba0.3MnO3 leads to an increase of the resistivity. The undoped sample (x=0) shows a metallic behavior, which can be fitted by the relation ρ(T)=ρ0+ρ2T2+ρ4.5T4.5, indicating the importance of electron-magnon scattering effects in this material. All the other samples (x≥0.10) are semiconductors throughout the studied temperature range (80-290 K). Several models have been used to fit their temperature-dependent resistivity: thermal activation, adiabatic nearest-neighbor hopping of small polarons (Holstein theory) and variable range hopping (VRH) models. The fits show that the electronic transport in semiconducting La0.7−xYxBa0.3Mn1−xFexO3 is well described and dominated by the VRH mechanism, for which the hopping distance (a) grows with increasing Fe3+ doping, thus increasing the average hopping energy W.