Quantitative evaluation and investigation of shielding coefficient and magnetic noise in stacked nanocrystalline magnetic shielding system

The utilization of nanocrystalline magnetic shielding can provide a low-noise weak magnetic environment for various ultra-high sensitivity measurements. Their interlayer insulation properties effectively impede eddy currents, thereby ameliorating eddy current losses and diminishing magnetic noise within the magnetic shielding structure. However, the nanocrystal's thin-layered structure and stacking process greatly impact its effective magnetic permeability and conductivity. Hence, this article presents a quantitative evaluation and research methodology for the shielding coefficient and magnetic noise in nanocrystal shielding systems, considering the influence of layer stacking. Firstly, the complex magnetic permeability of nanocrystal annulus with different stacking coefficients is measured, demonstrating a linear relationship. Secondly, based on the test results, a cubic nanocrystal shielding effectiveness model is constructed and validated against finite element results. Finally, an improved magnetic noise calculation model is analyzed and developed for square nanocrystal shielding bodies by utilizing the linear relationship and considering the truncation of eddy currents in different directions within the stacked nanocrystal shielding layer. The accuracy of the model is verified through experimental validation.