HIGH-SENSITIVITY SUPERCONDUCTING SENSOR FOR DIRECT MEASUREMENT OF FLUX-DENSITY

A novel magnetometer capable of direct measurement of flux densities o f several nanotesla is described. The sensing elements are ceramic sup erconductors. They cover a wide dynamic range (five orders of magnitud e) and are small (several millimeters in diameter and height). The phy sical principle is based on the nonlinear strong magnetic response of a superconductor to alternating magnetic fields and the linear depende nce on superimposed DC fields. The voltage at the second harmonic of t he driving frequency is directly proportional to the DC field to be me asured. A transfer function (dV/dB) of more than 500 VIT was obtained in a laboratory environment (including the Earth's field). The potenti al for ceramic superconductors to act as shields against magnetic fiel ds, are discussed.