Electronic transport in nanostructured films of La_0.67Sr_0.33MnO₃

Abstract

In this paper we report electronic transport in nanostructured films of the rare-earth manganite La_0.67Sr_0.33MnO₃. The films were grown by chemical solution deposition. The films show a resistivity peak in the temperature range of 250-265 K and have average grain size (∼50-60 nm). The grain size can be controlled by postdeposition annealing. The films also show a rise in resistivity at low temperature (T<40 K), reasonable low-field magnetoresistance up to 200 K, and nonlinear conductivity that shows up below 30 K. We ascribe these behaviors to the large number of natural grain boundaries that are present in these nanostructured films. We were also able to map the inhomogeneous local electronic properties arising from these grain boundaries using a variable-temperature scanning-tunneling microscope. We found that as the temperature is lowered, due to differences between the electronic properties of the grains and grain boundaries, the transport becomes more inhomogeneous. The nonlinear conduction as well as the low-field magnetoresistance in these nanostructured films closely resemble those in films with artificial grain boundaries.