Nonlinear Inductance of High Tc Superconducting Magnetic Core and Its Application to Quick Response Magnetic Sensors

Sensitive and quick-response nonlinear inductance characteristics were obtained for high-T
c
superconducting (YBa
2
Cu
3
O
7-x
) bulk cores at 77K, for which soft magnetic B-H hysteresis loops were observed. Nonlinear initial magnetization curves were analyzed using a flux penetration model, taking the demagnetizing coefficient into consideration. New quick-response magnetic devices such as magnetic modulators, magnetic switches, magnetic field sensors and current sensors were constructed using the high-T
c
superconducting cores of disk or toroidal shapes wound with polyester-coated copper wire coils. A sensor cutoff frequency of 700 kHz was obtained at a magnetizing frequency of 10 MHz.