EN
Epitaxial, textured, and polycrystalline La_{0.7}Ca_{0.3}Mn O_3 films, having about 150 nm thickness, were prepared by pulsed laser deposition techniques onto (110) NdGaO_3, MgO and lucalox substrates and investigated using 10 ns duration, 0.5 ns rise time electrical pulses having amplitude up to 500 V. Electroresistance of the films [R(E)-R(0)]/R(0) was investigated up to 80 kV/cm electric field strengths in temperatures ranging from 300 K to 4.2 K. Strong (up to 93%) negative electroresistance was obtained in polycrystalline La_{0.7}Ca_{0.3}MnO_3 films prepared on MgO and lucalox substrates. The epitaxial films grown on NdGaO_3 substrate demonstrated only a small resistance change due to Joule heating induced by a current pulse. It was concluded that electroresistance manifests itself in strongly inhomogeneous manganites films exhibiting a large number of structural imperfections producing ferromagnetic tunnel junction nets.