Continuous transition from weakly localized regime to strong localization regime in Nd_{0.7}La_{0.3}NiO_{3} films

We report an investigation of Metal Insulator Transition (MIT) using conductivity and magnetoconductance (MC) measurements down to 0.3 K in Nd_{0.7}La_{0.3}NiO_{3} films grown on crystalline substrates of LaAlO_{3} (LAO), SrTiO_{3} (STO), and NdGaO_{3}(NGO) by pulsed laser deposition. The film grown on LAO experiences a compressive strain and shows metallic behavior with the onset of a weak resistivity upturn below 2 K which is linked to the onset of weak localization contribution. Films grown on STO and NGO show a crossover from a Positive Temperature Coefficient (PTC) resistance regime to Negative Temperature Coefficient (NTC) resistance regime at definite temperatures. We establish that a cross-over from PTC to NTC on cooling does not necessarily constitute a MIT because the extrapolated conductivity at zero temperature \sigma_{0} though small (
Comment: 24 pages