Low frequency noise measurement in YBa₂Cu₃O_x thick films

The measurements of the low frequency noise near the transition temperature in YBa₂Cu₃O_x thick films having different shape of the superconducting resistive transition curve are reported. The results show that temperature dependence of the noise power is dependent on the resistive transition width. For the sample whose resistive transition is sharp, a single noise peak is observed near T_co. On the other hand, the sample, whose resistive transition is broad, exhibits two noise peaks near T_co and onset T_c. The investigation of the current and magnetic field dependence of the noise power suggests that the noise peak near T_co may be due to the vortex motion, while the noise peak near onset T_c may be associated with the thermal fluctuation.