Characteristics of a thick high-critical temperature superconductor film used as a highly sensitive magnetic sensor

In the construction of a highly sensitive magnetic sensor, the thick superconducting high-critical temperature superconductor (HTS) film will generally break the superconducting state of current flow at a value of current density J/sub ms/ greater than that of the critical current density J/sub c/ , when the resistance R/sub ms/ of the film to the flow of current occurs in the absence of an excitation magnetic field. The magnetic sensitivity S of the sensor when exposed to an excitation magnetic field, was found to be about 200%/(10/sup -4/ T) for Bi-Pb-Sr-Ca-Cu-O (BPSCCO) magnetic sensor, and about 7%(10/sup -4/ T) for Y-Ba-Cu-O (YBCO) magnetic sensor. That is, the magnetic sensitivity of the BPSCCO magnetic sensor is about 200 times greater than that of a giant magnetoresistance (GMR) sensor. Furthermore, after measurements through more than 300 thermal cycles between temperatures of 77.4 K and 300 K, the characteristics of the thick BPSCCO film magnetic sensor were found to exhibit no significant changes in magnetic response. The present paper reveals the dependencies of R/sub ms/ on the temperature T, of resistivity /spl rho/ of the thick film on J/sub ms/, of R/sub ms/ on the applied excitation magnetic field B/sub ex/, and the dependence of S on the /spl rho/.