Hopping conduction in double layered La2−2xCa1+2xMn2O7 manganite

Double layered La_2−2xCa_1+2xMn₂O₇ manganite has been synthesized using solid state reaction method for different dopant concentration x = 0.0–0.5. Their temperature dependence of resistivity (ρ − T) has been studied in the semiconducting region. The experimental observations were compared with the theoretically simulated temperature dependence of resistivity curves based on nearest neighbour hopping, Efros–Shklovskii variable range hopping, and Mott's 2D and 3D variable range hopping models. From the analysis of these results, Mott's 3D variable range hopping mechanism seemed to be most suitable mechanism describing the semiconducting behaviour of these double layered manganites. Temperature dependent activation energy also supported the Mott's 3D variable range hopping model. The Mott's activation energy was found to vary with the dopant concentration x and it showed a minimum value for x = 0.3.