Origin of the non-thermal photoresponse in thin films of two-phase manganites

Our studies of light-induced resistance changes (photoresponse) in thin films the colossal magnetoresistive manganite material (La,Pr)$_{0.67}$Ca$_{0.33}$MnO$_{3 }$experiments have revealed a non-thermal component of the light-induced resistance change .This non-thermal component is also observed in thin films of oxygen deficient La$_{0.67}$Ca$_{0.33}$MnO$_{3. }$The common feature of both these material systems is the co-existence of metallic and insulating phases. Our results indicate that this component may be associated with the light-induced resistance decrease in the insulating regions through an electronic mechanism. Previous studies have shown insulator-metal transitions induced by magnetic fields as well as electric fields in these materials. We will present our studies of the correlation of the observed non-thermal photoresponse with magnetoresistance as well as current-voltage characteristics.