Applicability of oxide superconductor to magnetic shielding

Magnetic shielding capability has been investigated on the Y-B-Cu-O oxide superconductor, aiming at a practical use of oxide superconductors. Critical-transport-current density and magnetization were measured using the four-terminal and electromagnetic methods at temperatures of 77 K and 4.2 K. The results indicated that the critical-current density by the transport measurement was two orders of magnitude lower than that by the magnetization. This means that the larger shielding currents were found to be induced in the grain. The magnetic field behind the disk-shaped specimen was measured using a magnetic sensor. The shielding capability does not depend upon the critical-current density derived from magnetization but the critical-transport-current density. The applicability of oxide superconductors to magnetic shielding is discussed.>