Title :
Direct detection of vortex motion in high-Tc grain boundary junctions
Author :
Hirano, S. ; Oyama, H. ; Matsuda, M. ; Morooka, T. ; Nakayama, S. ; Kuriki, S.
Author_Institution :
Res. Inst. for Electron. Sci., Hokkaido Univ., Sapporo, Japan
fDate :
3/1/2001 12:00:00 AM
Abstract :
Using a superconducting thin-film coil and Nb-based SQUID, the flux generated by vortices in a field-cooled (10 μT) wide bicrystal YBa2Cu3O7-δ grain boundary junction (GBJ) was measured directly at 77 K. At and above a small threshold field change, random switching noise was observed, with switching heights corresponding to long-distance movement of vortices over 20 to 500 μm within the GBJ, driven by the shielding current. The vortex movement was suppressed to lengths of less than 1 μm by making slots in the GBJ. From these results, we estimated the flux noise of a directly coupled dc SQUID magnetometer with a weak link in its pick-up coil
Keywords :
SQUID magnetometers; barium compounds; bicrystals; flux flow; grain boundaries; high-temperature superconductors; superconducting device noise; yttrium compounds; 10 muT; 77 K; Nb; Nb SQUID; YBa2Cu3O7-δ bicrystal; YBa2Cu3O7; direct flux detection method; directly coupled DC SQUID magnetometer; field cooling; flux noise; grain boundary junction; high-Tc superconductor; pick-up coil; random switching noise; shielding current; superconducting thin film coil; vortex motion; weak link; Current measurement; DC generators; Grain boundaries; Josephson junctions; Magnetic field measurement; Motion detection; SQUIDs; Superconducting coils; Superconducting device noise; Superconducting thin films;
Journal_Title :
Applied Superconductivity, IEEE Transactions on
