MEASUREMENTS OF NOISE AND TEMPERATURE-COEFFICIENT OF RESISTANCE ON YBA2CU3O7-DELTA THIN-FILMS IN MAGNETIC-FIELD

We measured low-frequency noise and temperature coefficient of resistance beta = (dR/dT)/R on YBa2Cu3O7-delta thin films at varying temperatures around superconducting transition. Magnetic field densities of 18-88 G were applied to the films. We found T(c) to decrease slightly with magnetic field even though beta at the respective T(c) remained constant. At the superconducting transition, the voltage noise power spectral density over the 10-1000 Hz frequency range decreased with magnetic field, whereas no change in noise behavior was observed with varying the magnetic field in normal state. At a constant temperature in transition, as the magnetic field density was varied, the noise magnitude followed the beta-2 dependence as predicted by the local thermal fluctuations theory of 1/f noise.