High temperature superconductors for low frequency magnetic shielding

The authors report the results of magnetic shielding measurements on pure YBa/sub 2/Cu/sub 3/O/sub 7- delta /, silver-doped YBa/sub 2/Cu/sub 3/O/sub 7- delta / packed powder, laser ablated thin film, and copper. The shielding factors of bulk ceramics were much higher than those of other materials and were not a function of frequency in the range from 10 Hz to 3000 Hz. Simply packed superconducting powder did not show any shielding. While polycrystalline ceramics were effective as shields, the thickness of the ceramic played a crucial role in shielding. The breakthrough field increased with thickness. The influence of DC fields on the shielding behavior depended on the magnitude of the fields.<>