77 K SQUIDs operating in the Earth´s magnetic field

Author

Sloggett, G.J. ; Foley, C.P. ; Lam, S. ; Binks, R.A. ; Dart, D.L.

Author_Institution

Div. of Appl. Phys., CSIRO, Lindfield, NSW, Australia

Volume

7

Issue

2

fYear

1997

fDate

6/1/1997 12:00:00 AM

Firstpage

3044

Lastpage

3047

Abstract

Weak magnetic fields like the Earth´s field (/spl sim/50 /spl mu/T) can adversely affect the operation of 77 K thin-film high-T/sub c/ SQUIDs through flux penetration into either the junction or the body of the SQUID. Josephson vortex penetration into the junction causes suppression of the critical current, increased white noise and possible cessation of normal SQUID operation. We have used various techniques to overcome this problem, including development of narrow (/spl sim/1 /spl mu/m wide) step-edge junctions with high critical current density. The adverse effects of Abrikosov vortex penetration into the SQUID include magnetic hysteresis and increased low-frequency noise. Film quality (J/sub c/) is found to be important In minimising these effects.

Keywords

SQUIDs; critical current density (superconductivity); geomagnetism; high-temperature superconductors; magnetic hysteresis; superconducting device noise; white noise; 77 K; Abrikosov vortex penetration; Earth magnetic field; Josephson vortex penetration; critical current density; flux penetration; low-frequency noise; magnetic hysteresis; step-edge junction; thin-film high-T/sub c/ SQUID; white noise; Australia; Critical current; Earth; High temperature superconductors; Magnetic field measurement; Magnetic fields; Magnetic flux; Noise measurement; SQUIDs; White noise;

fLanguage

English

Journal_Title

Applied Superconductivity, IEEE Transactions on

Publisher

ieee

ISSN

1051-8223

Type

jour

DOI

10.1109/77.621974

Filename

621974