Characterization of ramp edge-geometry Ag:YBa/sub 2/Cu/sub 3/O/sub 7-x//PrBa/sub 2/Cu/sub 3/O/sub 7-x//Ag:YBa/sub 2/Cu/sub 3/O/sub 7-x/ junctions and dc SQUIDs

Abstract

High-temperature superconducting Josephson junctions and dc SQUIDs were fabricated using a ramp edge-geometry SNS configuration. Ag-doped YBa/sub 2/Cu/sub 3/O/sub 7-x/ was used as electrodes and PrBa/sub 2/Cu/sub 3/O/sub 7-x/ as barrier. The I/sub c/R/sub n/ value of the junctions was in excess of 120 /spl mu/V at 75 K. The dc SQUIDs showed a flux modulation depth, /spl part/V//spl part//spl Phi/, over 150 /spl mu/V//spl Phi/, at 75 K. The flux noise of the devices, measured with dc bias currents operated at 75 K, showed a 1/f dependence at low frequency having values below 100 /spl mu//spl Phi//sub 0/Hz/sup - 1/2 / (the best values in the range of 30/spl sim/40 /spl mu//spl Phi//sub 0/Hz/sup - 1/2 /) at 1 Hz and less than 5 /spl mu//spl Phi//sub 0/Hz/sup - 1/2 / in the white noise region. The voltage modulation and magnetic field noise were 37 /spl mu/V and /spl sim/2 pTHz/sup - 1/2 / at 1 kHz for the directly-coupled dc SQUID magnetometers (with a pick-up loop 6 mm/spl times/ 3.5 mm) based on the ramp edge-geometry SNS configuration.