SQUID behavior at liquid nitrogen temperature in high-T c superconductors of the type Y-Ba-Cu-O

Abstract

Quantum interference at liquid nitrogen temperature in a bulk sample of high-Tc superconductor YBa2Cu3O9−y is described. The SQUID quantization loop is formed at random inside the sintered sample as an internal percolation loop with a Josephson weak link. The estimated values of this multiply connected quantization loop are: the inductance of the loopLSQ≈4×10−10 H, the critical currentIc≈1×10−6 A, the area of the loopA≈1×10−8 m2, and the hysteresis parameter β L ≈1. In the flux-locked loop regime the field sensitivity of this liquid nitrogen SQUID with a random loop is 10−9 T/Hz1/2 and the resolution is 5×10−3 Φ0/Hz1/2.