Charge-ordering in thin films of bilayered rare earth manganates

Thin films of bilayered manganates of the formula LnSr(2)Mn(2)O(7) (Ln=rare -earth), deposited on LaAlO3(100) substrates by nebulized spray pyrolysis, show charge-ordering transitions in the resistivity data. The transition te mperatures decrease from 205 K to 185 K as the rare-earth ionic radii decre ase from Ln=La to Gd. While magnetic-fields up to 6 tesla have little effec t on the charge-ordering transition, small electric currents prevent the on set of the charge-ordered state. Furthermore, the resistance decreases mark edly with increasing current, with nonlinear behavior, in polycrystalline f ilms deposited on Si(100) substrates. (C) 2000 Published by Elsevier Scienc e Ltd.