We have designed four multifunctional high-transition-temperature directly coupled superconducting-quantum-interference-device (SQUID) magnetometers on a 10×10 mm2 SrTi O3 bicrystal substrate. Each magnetometer is composed of two serial bare SQUIDs. These magnetometers can be connected to four kinds of first-order electronic planar gradiometers or two kinds of second-order electronic planar gradiometers by using analog subtracting electronic circuits. The noise spectra of each magnetometer, two first-order electronic planar gradiometers, and a second-order planar gradiometer were measured. We measured the small magnetic signal generated from a double D coil to show that this design could supplement the deficiency of a magnetometer.
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