Current-sensitive electroresistance and the response to a magnetic field in La_(0.8)Ca_(0.2)MnO_3 epitaxial thin films

摘要

The influence of a transport dc current on the resistivity of La_(0.8)Ca_(0.02)MnO_3 epitaxial thin films and their response to a magnetic field has been investigated. We found that when the applied dc current exceeds a threshold value, the electric resistivity in these films could be significantly enhanced. Such observations are completely repeatable. More attractive is that the enhanced resistance turns out to be sensitive to a weak current in a wide temperature range from 10 to 300 K. Even a very small dc current could remarkably depress the high resistance, showing a colossal electroresistance (ER) effect. ER reaches ～1175% at temperatures lower than ～50 K, and ～705% at 300 K for a current changing from 0.72 to 10.5 μA. A highly nonlinear behavior of the Ⅰ-Ⅴ curves persists even to room temperature. Significant influence of the magnetic field on the electric transports was also observed. It is found that a low field of 0.25 T could remarkably affect the Ⅰ-Ⅴ curves, resulting in a considerable magnetoresistance (MR).