EVIDENCE FOR TUNNELING AND MAGNETIC SCATTERING AT IN-SITU YBCO NOBLE-METAL INTERFACES

We report low-temperature conductance data for in situ YBa2Cu3O7-delta (YBCO)/Ag, YBCO/Au, and YBCO/Pt planar c-axis interfaces. Analysis of the conductance data for these interfaces, which have resistivities a s low as 1x10(-8) Omega . cm(2), indicates that tunneling is the predo minant transport mechanism. Zero-bias conductance peaks are present fo r all of the in situ interfaces. These peaks are analyzed in the frame work of the Appelbaum model and are attributed to the presence of isol ated magnetic spins at the interface. The presence and similarity of t he peaks for each noble-metal overlayer supports the hypothesis that t he magnetic spins are inherent to the YBCO surface.