70 K hysteretic Josephson effect in mesas patterned on (Bi,Pb)2Sr2CaCu2Oy single crystals

We report the engineering of sets of mesas on lead-substituted single crystals of Bi2Sr2CaCu2Oy. Each mesa behaves as a series array of intrinsic Josephson junctions with, up to 70 K, ‘‘two states’’ hysteretic I(V) characteristics, free of branching, whose RnIc products can be tuned through geometrical patterning and adjustment of the lead contents. RnIc values as high as 550 mV at 4.2 K have been reached. The tuning through lead substitution is attributed to the decrease of the anisotropy with increasing lead content.