High T/sub c/ superconducting magnetic multivibrators for fluxgate magnetic-field sensors

Sensitive and quick-response nonlinear inductance characteristics are found for high-T/sub c/ superconducting (YBa/sub 2/Cu/sub 3/O/sub 7-x/) disk cores at 77 K in which soft magnetic BH hysteresis loops are observed. Various fast-response magnetic devices such as modulators, amplifiers, and sensors are built using these cores. The magnetizing frequency can be set to more than 20 MHz, which is difficult to do with conventional ferromagnetic bulk materials such as Permalloy, amorphous alloys, and ferrite. New fast-response fluxgate-type magnetic-field sensors made from these cores, using AC and DC voltage sources, are presented. The former is used for second-harmonic type sensors, whereas the latter is for voltage-output multivibrator-type sensors. Stable, fast-response sensor characteristics were obtained for two-core multivibrators.<
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