Characteristics of a highly sensitive magnetic sensor constructed of a thick HTS film

For use in constructing highly sensitive magnetic sensors, the present authors have been studying the preparation of thick Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7-x/ (YBCO) films. In this research, thick YBCO film was fabricated as the magnetic sensor, constructed to retain a residual resistance R/sub res/ at the boiling point of liquid nitrogen (77.4 K). The resistance R/sub ms/ of the magnetic sensor, in the transition region /spl Delta/T, is found to be highly sensitive to the applied magnetic field B/sub ex/, where /spl Delta/T is the region of temperatures between the resistance drop T/sub c//sup onset/ and residual resistance T/sub c//sup res/ temperatures. Under temperature conditions of 77.4 K, the value of R/sub ms/ for this sensor (1.5 mm in width, 67 mm in length, and 280 /spl mu/m thick) for an applied B/sub ex/ of 80/spl times/10/sup -4/ T, increased by factor of 5.8 times greater than that in the absence of a magnetic held. In addition, no evidence was found of the existence of hysteresis in the R/sub ms/ vs B/sub ex/ characteristics for weak values of B/sub ex/. The present paper examines the fabrication conditions and magnetic responses of the highly sensitive sensor constructed of a thick YBCO film.