Transport studies of YBa2Cu3Oy/YxPr1−xBa2Cu3Oy and YBa2Cu3Oy/R0.7M0–3MnO3 superlattices, in which R=La or Nd, and M=Ca or Sr Original Research Article

We report the transport studies of YBa2Cu3Oy/YxPr1−xBa2Cu3Oy and YBa2Cu3Oy/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 structure. The resistive transition in a magnetic field shows thermal activated behavior. The flux pinning is reduced when the coupling strength between YBCO layers is decreased. The angular dependence of the critical current of YBa2Cu3Oy/PrBa2Cu3Oy superlattices reveals the dimensionality of superlattices. The magnetoresistance ratio (MR), |Δρ(H=7 T)−Δρ(H=0)|/Δρ(H=7 T), of YBa2Cu3Oy/R1−xMxMnO3 superlattices is affected by the layer coupling of R1−xMxMnO3 layers. The enhancement of the MR ratio in the tri-layer 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 ferromagnetic layers in magnetic fields. The results are discussed in terms of existing theories.