ZERO-FIELD FLUX NOISE IN GRANULAR BI2SR2CACU2O8

We report zero-magnetic field flux noise measurements on a granular Bi 2Sr2CaCu2O8 sample displaying the paramagnetic Meissner effect (PME). The spectral noise density, S-Phi(f), was measured in the frequency ra nge 0.04-400 Hz and for temperatures 0.5 < T/T-c < 1 (T-c = 85 K) usin g a custom made SQUID magnetometer. It is found that the noise density scales as S-Phi similar to 1/f(a) with a monotonously decreasing from a similar or equal to 1.3 at the lowest temperature to a similar or e qual to 1 as T-c is approached. The noise density exhibits its largest magnitude around T/T-c = 0.9. Using the fluctuation-dissipation theor em, good agreement is found between the measured noise power and the o ut-of-phase component of the ac susceptibility. The results favour a m odel with fluctuating spontaneous magnetic moments.