Magnetic Noise Modeling and Suppression in Composite Shields Based on Spatial Anisotropy and Residual Magnetization Measurement

Magnetic shielding devices (MSDs) play a crucial role in magnetoencephalography (MEG) measurements by providing an ultralow magnetic noise (MN) environment with a near-zero magnetic field, essential for detecting extremely weak neural signals. However, MN within MSDs typically exhibits spatial anisotropy, which is associated with the material’s residual magnetization (RM). Traditional measurement and modeling methods often fail to accurately reveal this relationship and are unable to effectively suppress MN. To address this issue, this study introduces a novel permalloy–nanocrystalline (P–N) composite structure and develops a MN calculation model that takes into account RM, anisotropy, and residual environmental noise. An RM measurement method based on finite element analysis and sensors is then established, enabling precise measurement of magnetic flux density and inversion of the spatial magnetization distribution, with MN calculated strictly in accordance with magnetic properties. The MN calculation at the center point along the north–south direction of the MSD showed an experimental error of only 3.68%. This research not only reveals the mechanisms underlying MN generation but also provides a new technological pathway for optimizing the magnetic shielding performance of ultrahigh-sensitivity atomic sensors.