JOSEPHSON BEHAVIOR OF VARIABLE THICKNESS BRIDGES IN TEXTURED YBA2CU3O7-DELTA

The i-V characteristics of textured yttrium barium cuprate have been measured using variable thickness bridges (VTBs) fabricated from bulk granular material. The results show the characteristic DC Josephson effect and, using microwave irradiation, the presence of integral and sub-integral Shapiro steps in the characteristics. In addition a strong field dependence of the critical Josephson current is also found. The V-H variation at various junction currents shows a well developed periodic structure with features that may be associated with flux trapping in itergranular regions. These features, combined with the temperature dependence of the Josephson current support the view that we are seeing the behaviour of a small number of Josephson junctions in these VTBs. Comparable measurements on non-aligned material do not show these effects, probably because of the wide range of intergranular misorientation across the bridge. © 1990.