Characterization of the low-frequency noise in high-temperature radio frequency superconducting quantum interference devices cooled in static magnetic fields

We have performed a study of the low-frequency noise in high-temperature radio frequency (rf) superconducting quantum interference devices (SQUIDs) cooled in static magnetic fields. At 77 K, the noise of different thin-film YB2C3O7-x washer rf SQUIDs was measured in static magnetic fields up to 55 mu T. The SQUID inductances ranged from 150 to 300 pH. The measured low-frequency flux noise of the SQUIDs S-Phi(1/2) at 1 Hz was between 70 and 350 mu Phi(0)/root Hz, and in terms of magnetic field noise S-B(1/ 2) between 120 and 1100 fT/root Hz. The low-frequency noise of all devices at 1 Hz showed no significant increase for all applied static fields. (C) 1999 American Institute of Physics. [S0003-6951(99)01306-6].