2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/28546We propose two statistical models for description the metal-insulator phase transition coupled with paramagnetic-ferromagnetic phase transition in manganites of the type La_{1-x}Sr_xMnO_3. The first one based on the competition of small polarons and delocalized carriers. In the second one the conductivity appears as a result of overlapping of large polarons. We compare our models with the experimental data.RevTeX 4 pages with 2 figuresMaterials Sciencetext