Electrical transport in the ferromagnetic and paramagnetic state of potassium-substituted manganites La_(1-x) K_x MnO_3 (x = 0.05, 0.1 and 0.15)

摘要

We report the analysis of resistivity in the ferromagnetic and paramagnetic state of La_(1-x) K_x MnO_3 (x = 0.05, 0.10 and 0.15). The phonon frequencies are estimated from the ab initio theory with calibrated Hamiltonian for the atomic interaction between a pair such as Mn-O and La/K-O including van der Walls interaction. The modified electron-phonon (acoustic and optic) scattering incorporating the statistical factor and electron-electron and electron-magnon interactions is effective to describe the resistivity behaviour for a temperatures less than the metal-insulator transition (T_P) in the ferromagnetic state of La_(1-x) K_x MnO_3 (x = 0.05, 0.10 and 0.15). The Mott-Ioffe-Regel criterion for metallic conductivity is valid, and k_F~? ~ 1,~ε_F~τ ~ 1. Paramagnetic semiconducting resistivity is consistent with small polaron conduction model, and variable-range hopping is inappropriate for the description of resistivity behaviour in a high-temperature region, T > T_P. The results suggest that disorder-induced localisation of charge carriers dominates electrical transport.