Flicker (1/f) noise in 45 degrees Bi-epitaxial grain boundary junctions and dc SQUID of YBa2Cu3Oy

We have fabricated dc superconducting quantum interference devices (SQUIDs) incorporating 45 degrees bi-epitaxial grain boundary junction, i.e. YBCO/Y SZ and YBCO/YBCO/YSZ, in washer geometry. The 1/f noise power of single jun ction comes from resistance fluctuation for high current bias and critical current fluctuation for low current bias. The noise spectrum of the de SQUI Ds was measured with dc and ac bias schemes and showed value of similar to 1 x 10(-5) Phi(0)/Hz(1/2) at 100 Hz. The possible noise sources, critical c urrent fluctuations, flux motion noise and resistance fluctuation, are inve stigated. The results are compared with previous published data.