The low-temperature magnetoresistance of La0.7Ca0.3MnO3 (LCMO) thin films has been investigated using a four-probe dc technique with a 5 T superconducting magnet. Thin film samples of LCMO were prepared in situ using a pulsed laser deposition technique. The results obtained from the high-resolution low-temperature (5-50 K) measurements, carried out on various samples differing widely in their resistivities, have shown distinct minima at Tm in the resistivity versus temperature plots for all fields. The depth of the resistance minima was found to increase with an increase in applied magnetic field H, while Tm versus H curves showed maxima at around 2 T. We have fitted the resistivity versus temperature data for all H to an expression that contains three terms, namely, residual resistivity, inelastic scattering, and electron-electron (e-e) interaction and Kondo effects. We conclude that the e-e interaction effect is the dominant mechanism for the negative temperature coefficient of resistivity of these colossal magnetoresistance (CMR) materials at low temperatures.
|Number of pages
|Physical Review B - Condensed Matter and Materials Physics
|Published - 1 Mar 2002