THE EFFECTIVE BARRIER THICKNESS IN RAMP-TYPE JUNCTIONS WITH A CONTINUALLY GRADED BARRIER OF Y_1-xPr_xBa₂Cu₃O_y

Ramp junctions have been successfully synthesized utilizing an Y_1-xPr_xBa₂Cu₃O_y barrier with a continually graded concentration of Pr. The properties of these junctions are dominated by the barrier material rather than the boundary. Also, the damaged ramp surface is excluded from the weak link region so its influence is minimized. The Josephson coupling occurs at the naturally formed S/N interfaces within the Y_1-xPr_xBa₂Cu₃O_y layer. Thus it leads to a highly transparent S/N boundary and greatly enhances the performance of the junctions. The effective thickness of the barrier can be varied even post fabrication, depending on the measuring temperature and the concentration gradient. The temperature dependence of the barrier thickness and Josephson properties were investigated and compared with those junctions with a conventional single barrier. These unique features should motivate further studies on the nature of these junctions.