Electrical resistivity of alkali metal doped manganites LaxAyMnwO3 (AÂ =Â Na, K, Rb): Role of electron-phonon, electron-electron and electron-magnon interactions

The electrical resistivity behaviour of alkali metal (Na, K, Rb) substitutions at La site in LaxAyMnwO3 (A = Na, K, Rb) manganites is studied caused by electron-phonon, electron-electron and electron-magnon scattering. Substitutions affect average mass and ionic radii of A-site and hence resulting lattice and optical phonon softening. Estimated resistivity compared with reported metallic resistivity, accordingly ρdiff. = [ρexp − {ρ0 + ρe-ph (=ρac + ρop)}], infers electron-electron and electron-magnon dependence over most of the temperature range. Electron-phonon contribution indicates that alkali metal K doping provoked larger lattice distortion, while electron-electron interaction is more dominating process for Na and Rb doped compound favouring motion of excess charge carrier. Semiconducting nature is discussed with variable range hopping and small polaron conduction model. The change in activation energies and the density of states at the Fermi-level is consistently explained by cationic disorder and Mn valence.