Development of a novel multi-constriction superconducting magnetic flux concentrator and its application in magnetoresistance-superconducting composite magnetic sensors

Abstract Magnetoresistance-superconducting composite magnetic sensors, as highly sensitive weak magnetic sensors, have broad application prospects in fields such as magnetocardiography, magnetoencephalography, and high-precision non-destructive testing. Among these, the magnetic field gain of the superconducting magnetic flux concentrator (MFC) is a key factor affecting the magnetic field resolution of magnetoresistance-superconducting composite magnetic sensors. However, current superconducting MFCs face the issue of saturation in magnetic field amplification performance. This paper proposes a novel superconducting MFC structure that enhances the magnetic field gain of the superconducting MFC by adopting a multilayer stacked structure of constrictions. Finite element simulations reveal the impact of different constriction stacking structure parameters on the magnetic field amplification capability. Based on this, a TMR-superconducting multi-constriction composite magnetic sensor with a double-layer constriction stacked structure was prepared. Compared to conventional TMR-superconducting composite magnetic sensors, the magnetic field sensitivity increased by more than 1.7 times. This superconducting MFC realizes a magnetic field gain of nearly 350 in a small volume, which boosts the magnetic field detection performance of traditional TMR from nT level to pT level at low frequencies. The research presented in this paper contributes to the development of high-sensitivity magnetoresistive sensors.