Low-frequency magnetic field penetration in HTSC ceramic

Penetration of a variable magnetic fields into high-temperature Y1Ba2Cu3O7-x ceramic superconductors is studied. Measurements of spatial distribution of low-frequency field and the depth of its penetration within 5-500 Hz frequency range at T=77 K are conducted. It is ascertained that in the presence of a constant field Ho the variable field penetration depth can be comparable with the sample sizes. The character of the variable field distribution is similar to the distribution of the earlier studied constant one. The variable field induction has a jump on the surface and is decreased gradually in the sample volume. In this case the constant magnetic field serves as a parameter, determining the critical current density in a sample