A novel HTS magnetometer, exploiting the low jc of bulk YBCO

The authors report a novel form of magnetometer which is based on the low critical magnetic field H_c1 of sintered samples of the high-temperature ceramic superconductor YBa₂Cu ₃O_y. By driving a sample of the superconductor around a magnetization hysteresis loop at a frequency of ~100 kHz and detecting the induced voltage in a coil coupled to the sample at the second harmonic of the drive frequency, they find that this voltage is linearly dependent on the applied DC magnetic field in which the sample is situated. They present a model which explains the operation of this magnetometer. The device, while not sensitive as a SQUID (superconducting quantum interference device), has the advantage of a wider dynamic range and direct measurement of flux density unlike a SQUID, which is only capable of sensing flux density changes. When operated at 77 K the prototype magnetometer has already demonstrated a sensitivity at least 10 times better than that of a commercial flux-gate magnetometer. The system also appears to provide a simple method for investigation of flux flow in these materials