High-Tc super conducting quantum interference devices with slots or holes: Low 1/f noise in ambient magnetic fields

High-transition temperature dc superconducting quantum interference devices (SQUIDs) have been fabricated with arrays of slots or holes patterned in the 186×204 μm2 washers. In two designs, with seven slots or 248 holes, the linewidth of the remaining YBa2Cu3O7−x film was 4 μm. These devices exhibited virtually no increase in their low-frequency noise when they were cooled in static magnetic fields up to a certain threshold, above 100 μT in the best case. Furthermore, the mutual inductance between these devices and a seven-turn, spiral coil was at least 85% of that for a solid SQUID with the same outer dimensions.