Physica C: Superconductivity and its applications

Noise characteristics of single grain boundary junction DC SQUIDs in Y1Ba2Cu3O7-δ films

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We have prepared DC SQUIDs in which the junctions are formed by the use of a single grain boundary between two single crystals in an epitaxial film of Y1Ba2Cu3O7-δ deposited onto an SrTiO3 bicrystal. The noise characteristics of the SQUIDs have been measured as a function of temperature and it is shown that below approximately 82 K noise is dominated by voltage noise across the junction and above this temperature by flux noise presumably from flux motion in the film. It is also found that at high temperatures where phase slippage across isolated individual junction is present the DC SQUID still performs well and this is attributed to synchronization of phase slippage between the two junctions of the SQUID connected by a superconducting loop. © 1990.