Abstract
The proposed application of magnetic sensors can be divided into those related to the direct measurement of very weak magnetic field, e.g., the biomagnetic field such as that of a magnetocardiogram (MCG), and those related to the measurement of other quantities by means of variations in the magnetic field, e.g., the force sensor used in automobiles and industrial robots. With this in mind, it is necessary to develop a highly sensitive magnetic sensor. In constructing such a highly sensitive magnetic sensor, the present authors have been studying the fabrication of bulk Bi-Pb-Sr-Ca-Cu-O (BPSCCO) as the magnetic sensor. This process makes use of the shock compaction method as a new fabrication technology of the bulk high-critical temperature superconductor (HTS). In the present paper, the criterion for fabricating a highly sensitive magnetic sensor is discussed when systematically changing the sensor thickness between 0.1 and 1.1 mm for sensors fabricated under a shock compaction pressure of 1 GPa. The magnetic sensitivity is found to be related to the value of thickness, and reached an approximate sensitivity value sensitivity of 400 %/(10-4 T) for the sensor with the thickness of 0.1 mm, being about 400 times that of a giant magnetoresitance (GMR) sensor. Experimental results revealed the dependencies of the sensitivity on sensor thickness, shock compaction pressure, and different BPSCCO particle size distributions. In addition, the present authors examined the voltage noise power (VNP) spectrum in order to clarify the voltage fluctuations of the magnetic sensors.
