Low-frequency noise reduction in YBa2Cu3O7 superconducting quantum interference devices by antidots

It is demonstrated that the low-frequency noise due to vortex motion in high-temperature superconducting quantum interference devices (SQUIDs) in ambient magnetic fields can strongly be reduced by a simple arrangement of antidots patterned into the SQUID. Sputter-deposited YBa2Cu3O7-delta radio-frequency SQUIDs (rf-SQUIDs) with step edge junctions are characterized before and after patterning of antidots in the vicinity of the Josephson junction. No deterioration of the rf-SQUIDs due to the introduction of the antidots can be detected. In contrary, the onset of the increase of the low-frequency noise in an applied magnetic field is shifted from 10 mu T for the bare SQUID to 40 (field cooled) and 18 mu T (zero-field cooled) for the rf-SQUIDs with antidots. The reduction of low-frequency noise in ambient field is explained by trapping of vortices by the antidots. The comparison of zero-field and field-cooled experiments demonstrates that flux penetrating the washer does not affect the low-frequency noise as long as the vortices are homogeneously distributed and the flux is properly pinned in the vicinity of the junction. (C) 2000 American Institute of Physics. [S0003-6951(00)04022-5]