We report the transport studies of Y-Ba2Cu3Oy/YxPr1-xBa2Cu3Oy and YBa(2)Cu(
3)Oy/R1-xMxMnO3 superlattices in magnetic fields in which R = La or Nd, and
M = Ca or Sr. The X-ray diffraction of samples shows superlattice structur
e. The resistive transition in a magnetic field shows thermal activated beh
avior. The flux pinning is reduced when the coupling strength between YBCO
layers is decreased. The angular dependence of the critical current of YBa2
Cu3Oy/PrBa2Cu3Oy superlattices reveals the dimensionality of superlattices.
The magnetoresistance ratio (MR), \ Delta rho (H = 7T) - Delta rho (H = 0)
\/Delta rho (H = 7T), of YBa2Cu3Oy/R1-xMxMnO3 superlattices is affected by
the layer coupling of R1-xMxMnO3 layers. The enhancement of the MR ratio in
the trilayer YBa2Cu3Oy/La0.7M0.3MnO3/YBa2Cu3Oy film in the low temperature
regime is significant and has a value of 33650% at T = 75 K. We attribute
this enhancement of the MR to the ordering of magnetic moment in ferromagne
tic layers in magnetic fields. The results are discussed in terms of existi
ng theories. (C) 2001 Elsevier Science Ltd. All rights reserved.