Magnetic signal scan imaging system based on giant magnetoimpedance (GMI) differential sensor

TL;DR

This paper introduces a high-sensitivity, room-temperature magnetic imaging system using differential GMI sensors, achieving superior noise suppression and spatial resolution for weak magnetic signals without magnetic shielding.

Contribution

The study presents a novel differential GMI sensor-based imaging system with enhanced noise performance and spatial resolution, outperforming conventional GMI and SQUID systems in unshielded environments.

Findings

Achieved noise spectral density of 46 pT/√Hz at 1 Hz

Demonstrated spatial resolution better than 200 micrometers

Validated effective weak magnetic field detection in unshielded settings

Abstract

This paper presents the design and implementation of a magnetic signal scanning and imaging system based on the giant magnetoimpedance (GMI) effect. The system employs a pair of performance-matched GMI sensing elements configured as a differential probe structure. Through co-optimized low-noise electronic and probe design, the system effectively suppresses both intrinsic sensor common-mode drift and external environmental magnetic noise, enabling high signal-to-noise ratio detection of nono-tesla to micro-tesla-level magnetic signals without magnetic shielding. Experimental results demonstrate that the differential system achieves significantly lower noise spectral density in unshielded environments compared to conventional GMI sensors (\SI{46}{pT}/$\sqrt{\text{Hz}}$ versus \SI{286}{pT}/$\sqrt{\text{Hz}}$ at \SI{1}{Hz}), with a sensitivity of 186,790 V/T and spatial resolution better than 200 micrometers. The system's excellent performance in weak magnetic field detection and spatial resolution was verified through scanning experiments of magnetic ink on US banknotes and magnetic reference samples. Compared to SQUID scanning systems, which requiring liquid helium cooling, this system based on the GMI effect offers advantages of room-temperature operation, compact structure, and low cost. Relative to conventional single-element GMI microscopes, it achieves significant improvements in signal-to-noise ratio and environmental adaptability. This research provides a practical solution for high-resolution magnetic field imaging at room temperature with broad application potential in materials magnetism, biomagnetic imaging, and nanomagnetic detection.