Characterization of flicker noise in YBa2Cu3O 7-δ bicrystal junctions in weak magnetic fields

Flicker noise in c-axis oriented long YBCO bicrystal grain boundary junctions was characterized as a function of temperature, biasing conditions and magnetic field applied perpendicular to the a-b plane over a wide range of temperatures from 15 K to over 70 K. Aperiodic variations, as a function of magnetic field, were observed in both the junction voltages, V_J, and the flicker noise magnitude under constant current bias as the magnetic field was scanned from 0-8 G. The noise magnitudes were found to peak at the minima of V _J. Analyses of the field dependencies of the magnitudes and the functional form of the voltage noise power spectra show that the noise did not arise from thermally activated flux motion. Based on the dependencies of the noise power spectra on the bias current and the dynamic resistance of the junction we conclude that the noise originates from the fluctuations of the critical current of the devices most likely due to trapping of carriers or defect motion within the grain boundary