Properties of the YBCO thin film interferometers fabricated on ZrO/sub 2/ bicrystal substrates

The properties of DC SQUIDs made of YBCO thin film deposited on ZrO/sub 2/ bicrystal substrate and the nature of the fabricated Josephson junctions have been studied. It is found that the characteristics of the junctions are similar to those of the SNS structures with paramagnetic impurities in the N layer. A level of interferometer noise close to 5*10/sup -4/ Phi /sub 0//Hz/sup 1/2/ and a magnetic field sensitivity of 10/sup -10/ T/Hz/sup 1/2/ at frequencies higher than 25 Hz in the usual feedback mode of the SQUID operation have been achieved at 77 K.