Dielectric permittivity and conductivity spectra of La 0.5Ca 0.5MnO 3 thin films presenting electric field induced metal–insulator transition

Abstract

Electric behavior of polycrystalline La 0.5Ca 0.5MnO 3 thin films, pulsed laser deposited on a (100) silicon substrate, is reported and discussed. An electrically induced metal-insulating transition around 150 K is found, which is voltage and thickness dependent. At low temperatures, the film conductivity is non-Ohmic and moderate electric fields lead to resistivity switching towards metaestable low-resistive states. Impedance spectroscopy measurements were also performed in order to determine the film dielectric permittivity and conductivity and to estimate the characteristic metal–semiconductor interface parameters. The obtained results show that the fraction of ferromagnetic metallic regions does not change when a voltage is applied, and that the mechanism responsible for the low temperature metal insulator transition and the conduction behavior is the appearance of connective paths due to the enhanced mobility of carriers activated by the electric field.