Mechanisms of noise increase in direct-coupled high Tc superconducting quantum interference device magnetometers exposed to magnetic fields

Koichi Yokosawa, Shinya Kuriki, Satoru Hirano, Hiroshi Oyama, Daisuke Suzuki, Keiji Tsukada

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

We have investigated the behavior of high-critical-temperature (high Tc) direct-coupled superconducting quantum interference device (SQUID) magnetometers in static and fluctuating magnetic fields. The magnetometers consist of narrow-linewidth superconducting films to prevent flux trap during field cooling. Moreover, they have no superconducting films crossing the bicrystal lines of the substrates (except at the Josephson junctions); i.e., they have no flux dams. When one of these magnetometers was cooled in a static magnetic field Bcool, the low-frequency noise when Bcool <100 μT was as low as that under zero-field cooling, but above 100 μT the noise increased substantially. On the other hand, when a field Bext of less than 4 μT was applied after zero-field cooling, the low-frequency noise increased in proportion to Bext. It returned to its original value reversibly when Bext was turned off. However, when Bext was greater than or equal to 4 μT, the output of the flux-locked-loop started to drift with time and the low-frequency noise increased further. This additional noise increase remained after turning off Bext. These results suggested that there are two modes of increase for the low-frequency noise induced by flux penetration due to the shielding current: a "reversible" mode and an "irreversible" mode. We found that the low-frequency noises of the two modes were additive with respect to their power, suggesting that the two noises derived from independent sources at different sites on the magnetometer. We also found that the reversible-mode noise could be reduced by improving the profile of the film edge.

Original languageEnglish
Pages (from-to)4049-4055
Number of pages7
JournalJournal of Applied Physics
Volume90
Issue number8
DOIs
Publication statusPublished - Oct 2001
Externally publishedYes

Fingerprint

magnetometers
interference
magnetic fields
low frequencies
superconducting films
cooling
dams
bicrystals
Josephson junctions
shielding
critical temperature
proportion
penetration
traps
output
profiles

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Physics and Astronomy (miscellaneous)

Cite this

Mechanisms of noise increase in direct-coupled high Tc superconducting quantum interference device magnetometers exposed to magnetic fields. / Yokosawa, Koichi; Kuriki, Shinya; Hirano, Satoru; Oyama, Hiroshi; Suzuki, Daisuke; Tsukada, Keiji.

In: Journal of Applied Physics, Vol. 90, No. 8, 10.2001, p. 4049-4055.

Research output: Contribution to journalArticle

Yokosawa, Koichi ; Kuriki, Shinya ; Hirano, Satoru ; Oyama, Hiroshi ; Suzuki, Daisuke ; Tsukada, Keiji. / Mechanisms of noise increase in direct-coupled high Tc superconducting quantum interference device magnetometers exposed to magnetic fields. In: Journal of Applied Physics. 2001 ; Vol. 90, No. 8. pp. 4049-4055.
@article{9a770967232145969a7e89b525e8e2f1,
title = "Mechanisms of noise increase in direct-coupled high Tc superconducting quantum interference device magnetometers exposed to magnetic fields",
abstract = "We have investigated the behavior of high-critical-temperature (high Tc) direct-coupled superconducting quantum interference device (SQUID) magnetometers in static and fluctuating magnetic fields. The magnetometers consist of narrow-linewidth superconducting films to prevent flux trap during field cooling. Moreover, they have no superconducting films crossing the bicrystal lines of the substrates (except at the Josephson junctions); i.e., they have no flux dams. When one of these magnetometers was cooled in a static magnetic field Bcool, the low-frequency noise when Bcool <100 μT was as low as that under zero-field cooling, but above 100 μT the noise increased substantially. On the other hand, when a field Bext of less than 4 μT was applied after zero-field cooling, the low-frequency noise increased in proportion to Bext. It returned to its original value reversibly when Bext was turned off. However, when Bext was greater than or equal to 4 μT, the output of the flux-locked-loop started to drift with time and the low-frequency noise increased further. This additional noise increase remained after turning off Bext. These results suggested that there are two modes of increase for the low-frequency noise induced by flux penetration due to the shielding current: a {"}reversible{"} mode and an {"}irreversible{"} mode. We found that the low-frequency noises of the two modes were additive with respect to their power, suggesting that the two noises derived from independent sources at different sites on the magnetometer. We also found that the reversible-mode noise could be reduced by improving the profile of the film edge.",
author = "Koichi Yokosawa and Shinya Kuriki and Satoru Hirano and Hiroshi Oyama and Daisuke Suzuki and Keiji Tsukada",
year = "2001",
month = "10",
doi = "10.1063/1.1403680",
language = "English",
volume = "90",
pages = "4049--4055",
journal = "Journal of Applied Physics",
issn = "0021-8979",
publisher = "American Institute of Physics Publising LLC",
number = "8",

}

TY - JOUR

T1 - Mechanisms of noise increase in direct-coupled high Tc superconducting quantum interference device magnetometers exposed to magnetic fields

AU - Yokosawa, Koichi

AU - Kuriki, Shinya

AU - Hirano, Satoru

AU - Oyama, Hiroshi

AU - Suzuki, Daisuke

AU - Tsukada, Keiji

PY - 2001/10

Y1 - 2001/10

N2 - We have investigated the behavior of high-critical-temperature (high Tc) direct-coupled superconducting quantum interference device (SQUID) magnetometers in static and fluctuating magnetic fields. The magnetometers consist of narrow-linewidth superconducting films to prevent flux trap during field cooling. Moreover, they have no superconducting films crossing the bicrystal lines of the substrates (except at the Josephson junctions); i.e., they have no flux dams. When one of these magnetometers was cooled in a static magnetic field Bcool, the low-frequency noise when Bcool <100 μT was as low as that under zero-field cooling, but above 100 μT the noise increased substantially. On the other hand, when a field Bext of less than 4 μT was applied after zero-field cooling, the low-frequency noise increased in proportion to Bext. It returned to its original value reversibly when Bext was turned off. However, when Bext was greater than or equal to 4 μT, the output of the flux-locked-loop started to drift with time and the low-frequency noise increased further. This additional noise increase remained after turning off Bext. These results suggested that there are two modes of increase for the low-frequency noise induced by flux penetration due to the shielding current: a "reversible" mode and an "irreversible" mode. We found that the low-frequency noises of the two modes were additive with respect to their power, suggesting that the two noises derived from independent sources at different sites on the magnetometer. We also found that the reversible-mode noise could be reduced by improving the profile of the film edge.

AB - We have investigated the behavior of high-critical-temperature (high Tc) direct-coupled superconducting quantum interference device (SQUID) magnetometers in static and fluctuating magnetic fields. The magnetometers consist of narrow-linewidth superconducting films to prevent flux trap during field cooling. Moreover, they have no superconducting films crossing the bicrystal lines of the substrates (except at the Josephson junctions); i.e., they have no flux dams. When one of these magnetometers was cooled in a static magnetic field Bcool, the low-frequency noise when Bcool <100 μT was as low as that under zero-field cooling, but above 100 μT the noise increased substantially. On the other hand, when a field Bext of less than 4 μT was applied after zero-field cooling, the low-frequency noise increased in proportion to Bext. It returned to its original value reversibly when Bext was turned off. However, when Bext was greater than or equal to 4 μT, the output of the flux-locked-loop started to drift with time and the low-frequency noise increased further. This additional noise increase remained after turning off Bext. These results suggested that there are two modes of increase for the low-frequency noise induced by flux penetration due to the shielding current: a "reversible" mode and an "irreversible" mode. We found that the low-frequency noises of the two modes were additive with respect to their power, suggesting that the two noises derived from independent sources at different sites on the magnetometer. We also found that the reversible-mode noise could be reduced by improving the profile of the film edge.

UR - http://www.scopus.com/inward/record.url?scp=0035886105&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0035886105&partnerID=8YFLogxK

U2 - 10.1063/1.1403680

DO - 10.1063/1.1403680

M3 - Article

AN - SCOPUS:0035886105

VL - 90

SP - 4049

EP - 4055

JO - Journal of Applied Physics

JF - Journal of Applied Physics

SN - 0021-8979

IS - 8

ER -