DETECTION OF MAGNETIC-FIELD BY MICROWAVE PROPERTIES OF HIGH-T(C) SUPERCONDUCTORS

Superconductors provide a wide spectrum of possibilities for sensing different physical effects and actual values or changes of physical quantities, because their fundamental properties are strongly influenced by external conditions. The development of high-T(c) ceramic superconductors in the form of bulk and film samples has broadened the applicability of these materials for various kinds of sensors and opened a way to design a new class of detectors. Based on some early measurements showing the strong dependence of the microwave properties of high-T(c) compounds on an external magnetic field, our first device application has been designed to control a thick-film microwave ring resonator by low magnetic field H. In this paper a new and sensitive magnetic-field detector is presented, which is developed from the previous work mentioned above. The quality factor Q of a high-T(c) superconducting ring resonator is observed to increase and then decrease with the increase of the field strength H in the low magnetic-field range. Q shows a huge change in the field interval 0-3 mT. The value of dQ/dH is 1 dB/18 muT. By using an HP Network Analyzer of 1 V/dB for this investigation, the accuracy of the measurement Of output voltage guarantees to detect the magnetic field with a sensitivity of 1-10 nT.