DC SQUID in YBaCuO ceramics operating at 77 K

Constrictions with typical cross-sectional areas of 10/sup -8/-10/sup -7/ m/sup 2/ engraved in bulk YBa/sub 2/Cu/sub 3/O/sub 7-d/ ceramics operate as DC SQUIDs (superconducting quantum interference devices) at 77 K. These sensors have a magnetic field sensitivity of 1 to 20 pT/ square root Hz, a flux sensitivity of 6*10/sup -6/ to 3*10/sup -5/ phi /sub 0// square root Hz, and a corresponding energy resolution in the 10/sup -30/-10/sup -29/ J/Hz range around 20 kHz. The noise spectral density of the device clearly exhibits low-frequency 1/f noise, which scales throughout the whole investigated range of frequencies. The noise spectra at 1 Hz varies between 5*10/sup -27/ and 2*10/sup -26/ J/Hz.<
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