Frequency dependence of electrical response of polycrystalline LCMO thin films

Abstract

Influence of strong electric field in wide frequency range (from DC to 35 GHz) on electrical resistance of thin La0.67Ca0.33MnO3 polycrystalline manganite films was investigated in the range of (78 divided by 300) K. Different behavior of resistance change vs. temperature was observed when pulsed DC electric field and microwaves were applied to the films. When pulsed DC electric field is applied the electric-field-induced resistance change ("electroresistance") of manganite film depended nearly monotonically on temperature. However, in microwave electric fields a non-monotonic character of the electroresistance temperature dependence was observed. The dependence of the electroresistance on quality of manganite films was observed in case of microwaves. The experimental findings are explained assuming different electrical current mechanisms in case of DC and microwave fields. The applied voltage drops mainly across the grains of polycrystalline film due to a presence of displacement currents in case of microwaves, whereas in DC case the voltage drop is across the grain boundaries.