OPERATION OF HIGH-SENSITIVITY RADIO-FREQUENCY SUPERCONDUCTING QUANTUMINTERFERENCE DEVICE MAGNETOMETERS WITH SUPERCONDUCTING COPLANAR RESONATORS AT 77 K

We have developed a novel coplanar resonator serving as a tank circuit for radio frequency washer superconducting quantum interference devic es (SQUIDs). Two coplanar lines surrounded the circular flux concentra tor washer, 13.4 mm in diameter, The SQUID, 3.5 mm in diameter, was co upled to the concentrator in the flip-chip configuration, All parts we re fabricated from single-layer epitaxial YBa2Cu3O7 films on LaAlO3 su bstrates. In this layout, the resonant frequency could be set between 600 and 850 MHz. With SQUID loops of 100X100 mu m(2) (SQUID) inductanc e L-s=150 pH or 10X500 mu m(2) (L-s=260 pH), we determined at 77 K whi te flux noise levels S-phi(1/2) of 1.0X10(-5) and 1.5X10(-5) phi(0)/ro ot Hz, respectively. Both figures corresponded to the field resolution of about 30 fT/root Hz. (C) 1997 American Institute of Physics.