Title :
(Hg,Re)1212 bicrystal grain boundary Josephson junctions and dc SQUIDs
Author :
Tsukamoto, A. ; Takagi, K. ; Moriwaki, Y. ; Sugano, T. ; Adachi, S. ; Tanabe, Kazuki ; Kandori, A.
Author_Institution :
Adv. Res. Lab., Hitachi Ltd., Tokyo, Japan
fDate :
6/1/1999 12:00:00 AM
Abstract :
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.
Keywords :
Josephson effect; SQUIDs; barium compounds; calcium compounds; grain boundaries; high-temperature superconductors; mercury compounds; rhenium compounds; superconducting device noise; superconducting thin films; 1 to 90 muV; 118 to 77 K; HgReBa/sub 2/Ca/sub 1/Cu/sub 2/O; I/sub C/R/sub n/ product; Josephson junctions; RSJ-like current-voltage characteristics; bicrystal grain boundary junctions; c-axis oriented; dc SQUIDs; feedback coil; field-induced periodic voltage; flux noise; flux-locked loop scheme; supercurrents; voltage modulation depths; Coils; Current-voltage characteristics; Feedback loop; Grain boundaries; Josephson junctions; SQUIDs; Substrates; Temperature; Transistors; Voltage;
Journal_Title :
Applied Superconductivity, IEEE Transactions on
