Magnetic field effect on YBCO/PBCO/YBCO Josephson junctions

Using magnetic field effects, the barrier-layer thickness dependence of the critical-current normal-resistance product (I/sub c/R/sub n/) of a-axis-oriented YBa/sub 2/Cu/sub 3/O/sub 7- delta //PrBa/sub 2/Cu/sub 3/ O/sub 7- delta //YBa/sub 2/Cu/sub 3/O/sub 7- delta / Josephson junctions exhibiting a clear magnetic field dependence has been experimentally obtained. Since the magnetic penetration depth of an a-axis-oriented thin film is large, the Josephson penetration depth of the junction easily becomes less than the junction-length, and the observed I/sub c/ is no longer equal to the product of the critical current density j/sub c/ and the junction area A when j/sub c/ approaches 1 kA/cm/sup 2/. The authors studied the magnetic field effects on the junction to evaluate the intrinsic I/sub c/ defined by j/sub c/A under such a condition, and evaluated the I/sub c/R/sub n/-values as j/sub c/AR/sub n/ by using the results. The maximum values of j/sub c/ and I/sub n/R/sub n/ were 310 A/cm/sup 2/ and 170 mu V, respectively, at 4 K for a junction with a 25-nm-thick PrBa/sub 2/Cu/sub 3/O/sub 7- delta /, barrier-layer. The intrinsic I/sub c/R/sub n/-value was found to increase exponentially with decrease in the barrier layer thickness.<
>