Electrical resistivity behaviour of sodium substituted manganites: electron-phonon, electron-electron and electron-magnon interactions

The present paper focuses on a quantitative analysis of the metallic and semiconducting behaviour of electrical resistivity in perovskite manganites La 1- x Na x MnO 3 (x=0.1, 0.17). An effective interionic interaction potential (EIoIP) with the long-range Coulomb, van der Waals (vdW) interaction and short-range repulsive interaction up to second neighbour ions within the Hafemeister and Flygare approach was formulated to estimate the Debye and Einstein temperature and was found to be consistent with the available experimental data. For both doping concentration x=0.1 and 0.17 the electron-phonon, electron-electron and electron-magnon interactions are effective to describe the resistivity behaviour for temperatures less than the metal-insulator transition (T P ). For temperatures, T > T P , the semiconducting nature is discussed with Mott's variable range hopping (VRH) model and small polaron conduction (SPC) model. The fitted density of states as revealed from VRH differs drastically from the experimental value and therefore means the VRH model is not a viable option for describing the resistivity behaviour in high temperature region, T > T P . The SPC model consistently retraces the higher temperature resistivity behaviour (T > θ D /2). The metallic and semiconducting resistivity behaviour of sodium substituted manganites are analysed, to our knowledge, for the first time highlighting the importance of electron-phonon, electron-electron, electron-magnon interactions and small polaron conduction. Copyright EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg 2010