Effect of sintering temperature on electrical transport properties of La0.67Ca0.33MnO3

A systematic study of electrical conductivity of all four materials was undertaken not only as a function of temperature (80-300 K), but also as a function of magnetic field up to 7 T mainly to understand the detailed conduction mechanism in these materials. On analyzing the data by using several theoretical models, it has been concluded that the metallic (ferromagnetic) part of the resistivity (ρ) (below TP) fits well with the equation ρ(T)=ρ0+ρ2.5T2.5, indicating the importance of grain/domain boundary effects (ρ0) and electron-magnon scattering processes (∼T2.5). On the other hand, in the high temperature (T>TP) paramagnetic insulating regime, the adiabatic small polaron and VRH models fit well in different temperature regions, thereby indicating that polaron hopping might be responsible for the conduction mechanism.