Frequency dependence of the intergranular magnetic flux penetration in ceramic $YBa_2Cu_3O_x$ uperconductor

Abstract

By means of small magnetic field ac susceptibility measurement at 10 kHz we found that the real and imaginary parts of ceramic $YBa_2Cu_3O_ x$ susceptibility in presence of the external low frequency field close to 0.1 Hz exhibit frequency dependence. The wide maximum of hysteresis losses and {\color{black} the exponential dependence} of the {\color{black} effectiveness of flux penetration} with increasing of external field frequency were obtained. We observed a nonlinear dynamic magnetic response in presence dc field and we suggest that this behavior is due to the dynamic and static Josephson vortex-vortex interaction.