Josephson effect in MgB/sub 2//Ag/MgB/sub 2/ step-edge junctions

Abstract

We have made MgB/sub 2//Ag/MgB/sub 2/ junctions using the steps formed on Al/sub 2/O/sub 3/(0001) substrates. The current-voltage characteristics of these superconductor-normal-superconductor (SNS) type Josephson junctions have shown nonhysteretic behavior with some excess current. The measured I/sub c/R/sub n/ values were 1.2 mV at 4.2 K and 0.24 mV at 20 K. We have observed the modulation of critical current under dc magnetic field as well as Shapiro steps under 20 GHz microwave irradiation.