Nonlinear effects in yttrium ceramic in a nonsteady-state magnetic field

Nonlinear electrodynamic properties in granular superconductors are studied for the case of yttrium ceramic in a nonsteady-state magnetic field and in the current state. A substantial increase in the amplitude of their even harmonics is observed. It is shown that the nonlinear properties are determined by an ensemble of vortices in the surface layer of the superconductor and depend on external influences.