Interpretation of metallic and semiconducting temperature-dependent resistivity of La1−xNaxMnO3 (x = 0.07, 0.13) manganites

In this paper, we undertake a quantitative analysis of the reported metallic and semiconducting behaviour of electrical resistivity in perovskite manganites La1−xNaxMnO3 (x = 0.07, 0.13). We have formulated an effective inter-ionic interaction potential (EIoIP) with the long-range Coulomb, van der Waals (vdW) interaction and the short-range repulsive interaction up to second neighbor ions within the Hafemeister and Flygare approach to deduce Debye (θD), and Einstein temperature (θE). The temperature-dependent resistivity for temperatures less than metal-insulator transition (TMI), is theoretically analysed within the framework of the classical electron-phonon model of resistivity. Due to inherent low-frequency acoustic phonon as well high-frequency optical phonons, the contributions to the resistivity have been estimated. For low doping (x = 0.07; TMI = 194 K), the electron-phonon interaction is sufficient to describe the resistivity behaviour. However, additional electron-electron scattering (power temperature dependence) contribution to resistivity is required for higher doping as x = 0.13 (TMI = 301 K). For temperatures, T > TMI, the semiconducting nature is discussed with Mott's variable range hopping (VRH) model and small polaron conduction (SPC) model. The SPC model consistently retraces the higher temperature resistivity behaviour (T > θD/2). The metallic and semiconducting behaviour of resistivity is theoretically discussed for the first time to our knowledge for La1−xNaxMnO3 in various compositions.