Effect of magnetic fields on the abnormal electroresistance behavior in epitaxial thin films

摘要

We report an unusual electroresistance (ER) behavior induced by a current and its response to magnetic fields in La_(0.8)Ca_(0.2)MnO_3 epitaxial thin films. These thin films were fabricated on SrTiO_3 (100) substrate using pulsed laser deposition (PLD) technique. It is found that the electric resistivity in these films is significantly enhanced by applying a dc current over a threshold value. Simultaneously, an abnormal electroresistance behavior appears in the temperature range from 10 to 300 K. The enhanced resistance turns out to be very sensitive to a weak current. Even a very small dc current can remarkably depress the high resistance, showing an unusual colossal ER effect. The ER reaches ～1175% at temperatures lower than ～50K, and ?705% at 300 K for a current changing from 0.72 to 10.5 μA. The influence of magnetic fields on the transport was also studied. The Ⅰ—Ⅴ curves can be strongly influenced by a low magnetic field even at room temperature. The deduced magnetoresis-tance (MR) reaches 120% at 300 K upon applying a magnetic field of 0.25 T. An interesting phenomenon is that the observed MR is current dependent.