Current-induced metallic behavior in Pr$_{0.5}$Ca$_{0.5}$MnO$_3$ thin films: competition between Joule heating and nonlinear conduction mechanism

摘要

Thin films of Pr0.5Ca0.5MnO3 manganites exhibiting charge/orbital-orderedproperties with colossal magnetoresistance have been synthesized by the pulsedlaser deposition technique on both (100)-SrTiO3 and (100)-LaAlO3 substrates.The effects of current-induced metallic-behavior of the films are investigatedas a function of the temperature and the magnetic field. Calculations based ona heat transfer model across the substrate, and our resistivity measurementsreveal effects of Joule heating on charge transport over certain ranges oftemperatures and magnetic fields. Our results also indicate that a nonlinearconduction, which cannot be explained by homogeneous Joule heating of the film,is observed when the material is less resistive (10-2 W.cm). The origin of thisbehavior is explained with a model based on local thermal instabilitiesassociated with phase-separation mechanism and a change in the long rangecharge-ordered state.