High-gain DC SQUID magnetometers with NbN nanobridges

Author

Irie, A. ; Hamasaki, K. ; Yamashita, T. ; Matsui, T. ; Komiyama, B.

Author_Institution

Dept. of Electron., Nagaoka Univ. of Technol., Niigata, Japan

Volume

27

Issue

2

fYear

1991

fDate

3/1/1991 12:00:00 AM

Firstpage

2967

Lastpage

2970

Abstract

High-gain DC SQUIDs using NbN nanobridges have been fabricated for magnetometers with high sensitivity, and their device parameters and intrinsic energy sensitivity have been evaluated. The slit inductance of the square washer SQUID was reduced by using the coplanar edge structure of the low inductance. The junction capacitance is typically 15~40 fF. The maximum voltage modulation is about 110 μV for the NbN nanobridge SQUID with an inductance of 0.18 nH. The maximum value of the transfer function |∂V/∂Φ| was ~1 mV/Φ₀, without matching circuit. The minimum intrinsic energy sensitivity is about 20 h at 50 kHz. The SQUID was operated in a usual flux-locked loop. The flux noise spectrum for a DC SQUID at 4.2 K in a superconducting Nb shield was 4×10^-5Φ₀|√Hz at 3 kHz and one order larger than the intrinsic flux noise. The critical current and |∂V/∂Φ| of these SQUIDs show no change after repeated thermal recycling and storage over 250 days

Keywords

SQUIDs; critical currents; flux flow; magnetic field measurement; magnetometers; niobium compounds; 15 to 40 fF; 42 K; DC SQUID magnetometers; NbN; coplanar edge structure; critical current; device parameters; flux noise spectrum; flux-locked loop; intrinsic energy; intrinsic flux noise; junction capacitance; matching circuit; nanobridges; sensitivity; slit inductance; square washer SQUID; storage; thermal recycling; transfer function; voltage modulation; Capacitance; Circuit noise; Critical current; Inductance; Nanoscale devices; Niobium; SQUID magnetometers; Superconducting device noise; Transfer functions; Voltage;

fLanguage

English

Journal_Title

Magnetics, IEEE Transactions on

Publisher

ieee

ISSN

0018-9464

Type

jour

DOI

10.1109/20.133833

Filename

133833