Minimizing magnetic fields of the combined magnetic shielding system for atomic comagnetometer

Spin-exchange relaxation-free atomic comagnetometer require a combined low-noise magnetic shielding system to provide a weak magnetic field environment. However, the remanent magnetization of the shielding materials themselves reduces the shielding performance, which necessitates suppression. This study addresses the demagnetization problem in magnetic shielding systems composed of µ-metal and MnZn ferrite by proposing a method based on optimizing the demagnetization function and minimizing the gaps between ferrite ring stacks to reduce the comagnetometer’s remanent magnetization. Experimental results demonstrate that the design achieves a magnetic field gradient of 0.94nTcm⁻¹ within ±3cm of the shielding cylinder’s axial range, with a minimum value of 0.28nT at the center. This performance significantly surpasses previously published results. Additionally, the long-term drift of the in situ magnetic field decreases with reduced remanent magnetization. The reduction in the shielding cylinder’s internal inhomogeneous magnetic field also suppresses atomic relaxation, thereby decreasing magnetic noise in the comagnetometer. This leads to a 14% reduction in rotation measurement sensitivity at 1Hz. This study helps ferrite ring stacks approach the remanent magnetization levels of monolithic ferrite designs, making combined low-noise magnetic shielding systems more applicable to high-precision quantum measurement fields, especially those requiring large ferrite components.