Nonlinear effects of current on transport in manganite films

Abstract

In films of ${\mathrm{La}}_{0.7}{\mathrm{Ca}}_{0.3}{\mathrm{MnO}}_{3}$ at current densities above about ${10}^{4}\phantom{\rule{0.3em}{0ex}}\mathrm{A}∕{\mathrm{cm}}^{2}$ a jump in resistance is found when the average sample temperature is just below the temperature of the maximum derivative of Ohmic resistance with respect to temperature. The jump is hysteretic as a function of current, temperature, and magnetic field. The existence of the jump is consistent with simulated effects of nonuniform Joule heating. Local thermometers based on noise features provide further evidence for the nonuniform heating. However, detailed comparison of the simulated Joule effects and the data show qualitative discrepancies, possibly due to strain-induced mixed-phase texture.