Title :
Nonlinear hysteresis in thin film SQUID magnetometers
Author :
Sun, J.Z. ; Gallagher, W.J. ; Koch, R.H.
Author_Institution :
IBM Thomas J. Watson Res. Center, Yorktown Heights, NY, USA
fDate :
3/1/1993 12:00:00 AM
Abstract :
Measurements on both YBaCuO- and Nb-based thin-film DC superconducting quantum interference device (SQUID) magnetometers reveal a nonlinear hysteresis at fields above 0.1 G. The nonlinear hysteresis is sensitive to sample temperature but insensitive to the time scale of the field sweep in the millisecond region. Such hysteresis can be accounted for by the nucleation and subsequent displacement of vortices at the edges of the SQUID input washer. A model has been developed that relates hysteresis to film current density. The model predicts an asymptotic quadratic field dependence, quantitatively consistent with the present data, and also predicts a threshold field which is suggested by the data.<>
Keywords :
SQUIDs; barium compounds; flux flow; high-temperature superconductors; magnetic hysteresis; magnetometers; niobium; yttrium compounds; HTSC; Nb; YBaCuO; asymptotic quadratic field dependence; displacement of vortices; film current density; model; nonlinear hysteresis; thin film SQUID magnetometers; threshold field; vortices nucleation; Hysteresis; Interference; Magnetic field measurement; SQUID magnetometers; Superconducting devices; Superconducting thin films; Temperature sensors; Thin film devices; Time measurement; Transistors;
Journal_Title :
Applied Superconductivity, IEEE Transactions on
