Study of Y-Ba-Cu-O dc SQUID devices with resistively shunted inductances

A number of dc SQUIDs with different inductance values have been fabricated in YBa/sub 2/Cu/sub 3/O/sub 7/ thin films on MgO substrates. Resistors prepared in Au thin films have been applied as shunt resistors for the SQUID inductance loop. Characterisation and noise measurement have been carried out on these SQUIDs. The results are in agreement with theoretical predictions of Enpuku et al. The use of shunt resistors has improved the performance of the SQUIDs with high inductance, and made it less dependent on the critical current of the junctions, which is not always reproducible. Furthermore, high SQUID inductance increases the coupling efficiency of magnetic flux, for example in terms of a better inductance matching between the SQUID and the pick-up loop in a directly coupled magnetometer. Based on this study, SQUID devices such as magnetometers and gradiometers with high field responses have been designed and tested.