Measurements and analysis of the noise spectral density of YBCO films

Abstract

We studied the voltage noise spectral density S V (f, T, H ) dependence on frequency f, temperature T and applied magnetic field H in YBa 2 Cu 3 O 7-δ films. The voltage noise spectral density S V (f ) as a function of frequency exhibits 1/f behavior according to a Lorentzian shape Awhere A, f 0 , B, C constants which are determined and compared for many values of H. The influence of temperature and magnetic field is clearly observed as a function of temperature, S V (T) is found to vanish at T g , the temperature of vortex glass transition, according to a (T -T g ) x law. We interpreted those results by the formation of a large distribution of glass vortex domains. Approaching T g , these domains grow in size and lifetime, while at T g those parameters diverge.