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-Tc superconducting YBa2Cu3Oy thin film. The range of the measuring temperature T was from 11 to 90 K. It is found that the noise power spectrum curves all overlap and decrease smoothly as the frequency f increases for T < 84.3 K whereas a transition begin to develop as T > 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 suggests that the noise may come from the resistance fluctuation which is caused by the thermal fluctuation. The causes will be also discussed in terms of the flux motion of the high-Tc superconductors.
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