VOLTAGE VERSUS FLUX RELATION OF HIGH T(C) DC SUPERCONDUCTING QUANTUM INTERFERENCE DEVICE WITH DIFFERENT INDUCTANCES

The voltage versus flux (V-PHI) relation of dc superconducting quantum interference devices (SQUIDs) in the presence of thermal noise at T=77 K is studied. A theoretical expression for the modulation-voltage DELTAV in the V-PHI relation is presented as a function of SQUID inductance. The theoretical expression is compared with experimental results of DELTAV reported recently for high T(c) SQUIDs with different inductances. It is shown that experimental results agree quantitatively with theoretical ones. It is also shown that imperfection of Josephson junctions degrades the modulation voltage more significantly when the inductance increases. The dependence of the modulation voltage on the inductance clarified in the paper is useful for developing a magnetic sensor using the SQUID.