TEMPERATURE-DEPENDENT NOISE IN YBA2CU3OY THIN-FILM

We measured the noise power spectral density at a constant current (3 mA in this report) and various temperatures to study the origin of the noise in the high-T-c superconducting YBa2Cu3Oy thin film. The range of the measuring temperature T was from 11 to 90 K. It is found that t he noise power spectrum curves all overlap and decrease smoothly as th e frequency f increases for T < 84.3 K whereas a transition begin to d evelop as T greater than or equal to 84.3 K, then drop after T > 85.6 K. Furthermore, the temperature dependent noise power density at f = 0 .2 Hz can be fitted to the thermal fluctuation model. This result sugg ests that the noise may come from the resistance fluctuation which is caused by the thermal fluctuation. The causes will be also discussed i n terms of the flux motion of the high-T-c superconductors.