An in-depth insight at the percolation model and charge transport mechanism in La_0.7Ca_0.1Pb_0.2Mn_1-2xAl_xSn_xO₃ manganite prepared by sol–gel route

In this work, we presented our results on the electrical and magnetoresistance characteristics of La_0.7Ca_0.1Pb_0.2Mn_1-2xAl_xSn_xO₃ (x equal to 0 and 0.025) prepared using the sol–gel method. X-ray diffraction (XRD) analysis revealed that all samples crystallize in Rhombohedral structure with R-3c space group. In addition, to obtain further information regarding the electrical properties, we performed resistance versus temperature ρ (T) measurements under different applied magnetic fields using a standard four-probe technique. The resistivity data, represented as ρ (μ₀H, T), indicated the presence of a transition from metal to semiconductor state. As the magnetic field increases, the maximum resistivity values decrease, and the temperature (T_M-SC) at which the transition from insulator to metal occurs rises. In the temperature range where T is less than T_M–SC, the electrical resistivity ρ (T) was modeled as ρ(T) = ρ₀ + ρ₂T² + ρ_4.5T^4.5, signifying that the transport behavior is influenced by a combination of interactions involving electron–magnon, electron–phonon and electron–electron scattering processes. Conversely, in the temperature range exceeding T_M–SC, the transport mechanism was elucidated through the utilization of adiabatic small polaron hopping and variable-range hopping models. To improve understanding of the variations in the resistivity profile across the temperature range, ρ (T) was fitted using the percolation model. Additionally, research was conducted on the magnetoresistance effect (MR %). The highest magnetoresistance values are observed around the temperature T_M–SC.