CHARACTERIZATION OF YBA2CU3O7 PRBA2CU3O7 SUPERLATTICES/

We investigated the structural and superconducting properties of c-axi s oriented (YBa2CU3O7)nY/(PrBa2Cu3O7)nPr superlattices with thicknesse s of the individual layers down to one unit cell (10 greater-than-or-e qual-to nY greater-than-or-equal-to 1; 18 greater-than-or-equal-to nPr greater-than-or-equal-to 1). By transmission electron microscopy and X-ray diffraction we find an excellent structural quality of the sampl es, though the quantitative analysis shows the existence of defects. I n superlattices with decoupled YBa2Cu3O7 layers of two unit cell thick ness we find a high T(c) value of 75 K. We probed the flux line struct ure in the superlattices by measurements of the critical current densi ty in magnetic fields. The experiments show that the flux-line dynamic s is dominated by the movement of pancake vortices.