title: Magnetic flux noise in dc SQUIDs: temperature and geometry dependence.
abstract: The spectral density S(Φ)(f) = A(2)/(f/1 Hz)(α) of magnetic flux noise in ten dc superconducting quantum interference devices (SQUIDs) with systematically varied geometries shows that α increases as the temperature is lowered; in so doing, each spectrum pivots about a nearly constant frequency. The mean-square flux noise, inferred by integrating the power spectra, grows rapidly with temperature and at a given temperature is approximately independent of the outer dimension of a given SQUID. These results are incompatible with a model based on the random reversal of independent, surface spins.
authors.affiliation: Department of Physics, University of California, Berkeley, California 94720-7300, USA.
authors.forename: S M
authors.initials: SM
authors.lastname: Anton
authors.affiliation: Department of Physics, University of California, Berkeley, California 94720-7300, USA.
authors.forename: J S
authors.initials: JS
authors.lastname: Birenbaum
authors.affiliation: Department of Physics, University of California, Berkeley, California 94720-7300, USA.
authors.forename: S R
authors.initials: SR
authors.lastname: O'Kelley
authors.affiliation: MIT Lincoln Laboratory, 244 Wood Street, Lexington, Massachusetts 02420, USA.
authors.forename: V
authors.initials: V
authors.lastname: Bolkhovsky
authors.affiliation: MIT Lincoln Laboratory, 244 Wood Street, Lexington, Massachusetts 02420, USA.
authors.forename: D A
authors.initials: DA
authors.lastname: Braje
authors.affiliation: MIT Lincoln Laboratory, 244 Wood Street, Lexington, Massachusetts 02420, USA.
authors.forename: G
authors.initials: G
authors.lastname: Fitch
authors.affiliation: MIT Lincoln Laboratory, 244 Wood Street, Lexington, Massachusetts 02420, USA.
authors.forename: M
authors.initials: M
authors.lastname: Neeley
authors.affiliation: National Institute of Standards and Technology, Boulder, Colorado 80309-044, USA.
authors.forename: G C
authors.initials: GC
authors.lastname: Hilton
authors.affiliation: National Institute of Standards and Technology, Boulder, Colorado 80309-044, USA.
authors.forename: H-M
authors.initials: HM
authors.lastname: Cho
authors.affiliation: National Institute of Standards and Technology, Boulder, Colorado 80309-044, USA.
authors.forename: K D
authors.initials: KD
authors.lastname: Irwin
authors.affiliation: Department of Physics, University of Maryland, College Park, Maryland 20742, USA.
authors.forename: F C
authors.initials: FC
authors.lastname: Wellstood
authors.affiliation: MIT Lincoln Laboratory, 244 Wood Street, Lexington, Massachusetts 02420, USA.
authors.forename: W D
authors.initials: WD
authors.lastname: Oliver
authors.affiliation: Institut für Theorie der Kondensierten Materie, Karlsruhe Institute of Technology, D-76128 Karlsruhe, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Shnirman
authors.affiliation: Department of Physics, University of California, Berkeley, California 94720-7300, USA.
authors.forename: John
authors.initials: J
authors.lastname: Clarke