Study on the frequency response characteristic of superconducting/tunnel magnetoresistance composite magnetic sensors

Abstract

The superconducting/tunnel magnetoresistance (TMR) composite magnetic sensor is expected to have great application prospects in the field of weak magnetic field detection due to its ultra-high detectivity. For some special applications such as bio-magnetic measurement, it is of necessity to study the frequency response characteristic. Therefore, a superconducting/TMR composite sensor was fabricated and its frequency response was systematically studied in this paper. Firstly, the sensitivity of composite magnetic sensors was found to decrease rapidly with the magnetic field frequency. After excluding the influence of the TMR device itself at different temperatures, the sensitivity decay with magnetic field frequency was attributed to the AC loss of the superconducting loop. Finally, the minimum detectable field of the composite magnetic sensor was obtained by combining the sensitivity and noise spectrum. The sensor exhibits superior magnetic field detectivity, particularly in the low-frequency range, which indicates the suitability for the application of bio-magnetic field detection.