Abstract
The magnetic shielding effect of Ba2YCu3O7-δ, Cu and Fe-Ni plates was examined as a function of the frequency of applied ac magnetic field using magnetic heads. The effect of Ba2YCu3O7-δ plates was superior to that of Cu and Fe-Ni plates in the low-frequency (< 5 kHz) region at 77 K, while in the high-frequency (> 10 kHz) region, the effect of Ba2YCu3O7-δ plates was almost the same or slightly inferior to that of Cu plates. The shielding effect of Ba2YCu3O7-δ plates was strongly affected by the micro cracks and porosity of the samples. The magnetic shielding effect of Ba2YCu3O7-δ plates decreased rapidly with applied dc magnetic field, while the effect of Cu and Fe-Ni plates did not change with the application of dc magnetic field.