Integrated high-transition temperature squid-based voltmeters operated at 77 k

H. C. Yang*, J. H. Chen, H. E. Horng, S. Y. Yang, J. T. Jen

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


The voltage noise levels of high-Tc based YBa2Cu3Oy bicrystal SQUIDs and SQUID voltmeters were measured to investigate their noise characteristics. The SQUIDs are of washer type with outer dimension of 90 μm × 90 μm and inner dimension of 20 urn x 20 um. The SQUIDs have a normal inductance of about 60 pH. The integrated modulation and input coils were circular in shape. The modulation coil has a radius of r2 = 80 u.m and r, = 60 [im while the input coil for voltage measurement has radius r, = 50 urn and r, =30 (im. Using a dc bias and standard flux locked loop, the spectral density of the voltage noise, Sv, was observed to behave as I/fat low frequencies and the root mean square flux noise, S2, is white and has a value of ~15 nO0/Hz2 at l kHz. The flux noise levels were reduced to ~ 4 ii-4yHz2 using the ac bias reversing technique. These data suggest that the dominant 1/f voltage noise was caused by critical current fluctuations. We further demonstrate that the 1/f can be induced by flux motion. The voltage noise levels of the SQUID voltmeters are also reported.

Original languageEnglish
Pages (from-to)4412-4415
Number of pages4
JournalIEEE Transactions on Applied Superconductivity
Issue number2 PART 3
Publication statusPublished - 1999

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Electrical and Electronic Engineering


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