(Hg,Re)1212 bicrystal grain boundary Josephson junctions and dc SQUIDs

Bicrystal grain boundary junctions and dc SQUIDs are fabricated using c-axis oriented (Hg,Re)-1212 thin films grown on 24/spl deg/ SrTiO/sub 3/ bicrystal substrates, The junctions exhibit supercurrents up to a temperature close to the film T/sub c/ of 118 K and RSJ-like current-voltage characteristics. A large I/sub C/R/sub n/ product of 400-460 /spl mu/V is observed at 77 K in some junctions. The dc SQUIDs show a field-induced periodic voltage up to 111 K. The 18 pH-SQUID exhibit voltage modulation depths as large as 90 /spl mu/V (at 77 K), 27 /spl mu/V (at 97 K), and 1-2 /spl mu/V (at 110 K). The SQUID with a feedback coil is operated in a flux-locked loop scheme and shows flux noise of 10/sup -3/ /spl phi//sub 0//Hz/sup 1/2/ at 1 Hz.