Readdressing the issue of low-temperature resistivity minimum in La0.7Ca0.3MnO3 thin films

We have investigated the origin of low-temperature resistivity minima observed in epitaxial thin films of La_0.7Ca_0.3MnO₃ (thicknesses—300 Å and 3000 Å) using electrical and magneto-transport property measurements. We observe considerably smaller hysteresis in the magnetoresistance measurements for the thicker film than the thinner film. 300 Å film shows meta-stability in the resistivity measurements at low temperature and for this film the sample current ‘I’ shows large effect on the resistivity and its minima temperature. These observations suggest that the strain induces electronic intra grain inhomogeneity in these samples and these inhomogeneities consist of regions of different resistive phases. It appears that the high resistive phase prevents the transport of charge carriers between two low resistive regions thus giving rise to the resistivity minimum in these samples.