Photoconductivity in manganites

We report two types of photoconductivity effects observed by illumination o f oxygen deficient manganites thin films with UV or visible light. One is t he persistent photoconductivity effect observed at low temperature (T < 30 K) when the thin film is in the metallic state. This effect is analog to th e persistent photoconductivity observed in the high T-c superconductors par ticularly in oxygen deficient YBaCuO thin films. The other type of effect i s a photoinduced transition to metallic state at temperatures T < 100 K obs erved in Pr2/3Sr1/3MnO3 thin film which stays always in the semiconducting state in the darkness. This photo induced metallic transition from a semico nducting state leads to a non persistent colossal photoconductivity (severa l orders of magnitude of decrease of the resistivity).