A Range Extension Method for Superconducting/TMR Composite Magnetic Sensors

The superconducting/tunneling magnetoresistance (TMR) composite magnetic sensor is regarded as a promising candidate for weak magnetic field measurement due to its exceptional sensitivity. However, its measuring range is limited to the order of microtesla, constrained by the critical current density of superconducting materials, which hinders its application in the geomagnetic environment. To address this issue, a method for extending the range through the application of a pulse-modulated magnetic field when the sensor is close to saturation was first proposed in this article. Furthermore, a linear interval truncation approach was introduced to mitigate the nonlinear effects derived from the TMR and superconducting intrinsic properties. The final experimental results demonstrated that the linear working range of composite sensors was extended from 6000 to 20 000 nT, while maintaining a relatively low nonlinearity of 1.8%, thereby validating the feasibility and efficacy of the range extension method. The work presented in this article extends the application of high-performance superconducting/TMR composite magnetic sensors.