Large negative magnetoresistance in thin films of magnetic material Bi2-xPbxSr3Co2O9

We have studied the effect of Pb substitution on the transport properties of nonmagnetic layered cobalt-oxide Bi2Sr3Co2O9 prepared by the molecular beam epitaxy technique. All the films were prepared on YAlO3 (001) and Nd:YAlO3 (001) substrates in the presence of pure ozone. The film without Pb substitution shows a highly insulating behavior. Pb substitution makes the film more conductive and increases its c-axis length. The most striking effect of Pb substitution is the appearance of large negative magnetoresistance typically below 10 K. We propose that this material can be used in the fabrication of a Bi2Sr2Can-1CunO4+2n+delta-based functional device.