Enhanced magnetoresistance in YBa2Cu3O7/Nd0.7Sr0.3MnO3 heterostructures using magnetic flux focusing

Enhanced low field magnetoresistance (MR) in Nd0.7Sr0.3MnO3 (NSMO) has been achieved by using high-T-c superconducting flux focusing devices made of YBa2Cu3O7(YBCO)/NSMO heterostructures. Two kinds of flux focusing schemes, gap, and washer devices, have been used where an applied magnetic field is expelled from patterned YBCO pads and focused onto a bridge of NSMO film. Using such a magnetic lens, at temperatures below 77 K similar to 800%, enhancement in MR=-(R(H)-R(0))/R(0) was observed for different samples. This corresponds to more than 10% change in the MR of NSMO in the presence of 200 G. For the maximum MR response in NSMO, the YBCO/NSMO heterostructures were deposited on (100) LaAlO3 substrate by pulsed laser deposition in situ so that the peak resistance temperature (T-p) of NSMO was below the superconducting transition temperature (T-c) of YBCO. (C) 1996 American Institute of Physics.