| The character of charge carriers in the manganites can be changed to n-type by replacing La3+ with tetravalent ions like Ce, Sn, Zr etc. A combination of n- and p-type oxides can form a p-n junction that can be used as a functional device for various applications. Therefore, the recently developed n-type La-Sn-Mn-O compound has attracted much research interest. We have synthesized the (La1-xSnx)2Mn2O7 (x = 0.1,0.2 and 0.3) in bulk form using solid state reaction route. These samples were characterized using x-ray diffraction and temperature dependence resistivity measurements. Rietveld analysis is performed using the FULLPROF code to ensure the single phase nature of the samples. PowderX technique is used for peak indexing and to determine the lattice parameters. The variation in lattice parameters has been observed and the unit cell volume increases with the increase in Sn concentration. The metal-insulator transition is observed for all the samples. We have fitted our resistivity data for the different temperature ranges, with the help of theoretical models. At low temperatures below transition temperature (Tc), the data fits well with the expression: p = p0 + p1T2.5. This suggests that electron-electron, electron-phonon, and electron-magnon interactions are responsible for variation in resistivity below Tc. The higher temperature data follows the relation: p(T) = p0T exp(Ea/kBT). This shows that the conductivity above the transition temperature is due to small polaron hopping. |
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