ENHANCEMENT OF LOW-FIELD MAGNETORESISTANCE IN YBA2CU3O7 ND0.7SR0.3MNO3 HETEROSTRUCTURES/

In order to obtain an enhancement of low field magnetoresistance (MR) in Nd0.7Sr0.3MnO3 (NSMO) films, two kinds of superconducting flux focu sing devices made of YBa2Cu3O7 (YBCO) have been fabricated. In the sup erconducting state, YBCO expels magnetic flux from its interior and fo cuses the magnetic flux on a bridge of NSMO film. Using such a magneti c ''lens'', at temperatures below 77 K, similar to 900% enhancement in MR was observed. This corresponds to more than 15% change in the MR o f NSMO in the presence of a couple of hundred Gauss. In order to succe ssfully integrate high-T-c superconductivity with the magnetoresistive effect, bilayers of YBCO/NSMO were in situ deposited on (100) LaAlO3 substrates by pulsed laser deposition so that the peak resistance temp erature (T-p) of NSMO was below the superconducting transition tempera ture (T-c) of YBCO. X-ray diffraction and Rutherford Backscattering Sp ectroscopy (RBS) measurements provide evidence of epitaxial growth of YBCO/NSMO heterostructures.