Meyer-Neldel rule in the conductivity of manganite single crystals

The Meyer-Neldel behavior of conductivity of low-doped manganite ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Ca}}_{\mathit{x}}{\mathrm{MnO}}_{3}$ single crystals has been investigated. The evolution of the isokinetic temperature of conductivity, modified by Ca-doping, hydrostatic pressure, and current bias has been determined. In addition, the evolution of isokinetic temperature with ageing has also been studied. The Meyer-Neldel behavior of the manganite system stems from the multiexcitation entropy mechanism. The isokinetic temperature turned out to be a sensitive parameter characterizing changes in the transport properties of mixed valence manganites, which in the presence of a detailed theoretical model of the excitations coupling in manganites could become a powerful tool for the characterization and investigation of transport properties of manganites.