Electric-field-induced melting of the randomly pinned charge-ordered states of rare-earth manganates and associated effects

Films of charge-ordered Nd0.5Ca0.5MnO3, Gd0.5Ca0.5MnO3, Y0.5Ca0.5MnO3, and Nd0.5Sr0.5MnO3 show insulator-metal transitions on the passage of small ele ctrical currents. That such an electric-field-induced transition occurs eve n in Y0.5Ca0.5MnO3 where the charge-ordered state is not affected by magnet ic fields is noteworthy. The transition is attributed to the depinning of t he randomly pinned charge solid. These materials also exhibit an interestin g memory effect probably due to the randomness of the strength as well as t he position of the pinning centers.