Unshielded Magnetorelaxometry of Nanogram-Scale Magnetic Particles With an YIG-Based Gradientometer System

This work presents a novel YIG-based gradientometer system specifically designed for high-performance magnetorelaxometry (MRX) applications. The two-channel impedance-based yttrium-iron garnet (IM-YIG) sensor achieves an exceptional magnetic field sensitivity of 10pT/√Hzcombined with ultrafast (less than 1 ms) dead time, enabling precise measurement of rapid magnetic particle relaxation dynamics. The gradiometric configuration provides effective common-mode interference rejection while maintaining a wide dynamic range essential for MRX studies. The developed system demonstrates several key advantages over traditional approaches: it operates at room temperature without requiring cryogenic infrastructure or complex optical components, significantly simplifying experimental setups while improving measurement stability, and works without magnetic shielded environment. Comprehensive testing with magnetic particle samples verified the system’s capability to reliably detect relaxation signals corresponding to iron masses as low as 50 ng. Furthermore, analysis of baseline stability suggests potential for even lower detection limits through optimized signal processing. The system’s robust performance and simplified architecture make it particularly suitable for deployment in resource-constrained environments where conventional SQUID or OPM systems would be impractical.