Modeling and Application of Magnetic Shaking for Improving Permeability and Performance of Magnetic Shields

Biomagnetic field measurements necessitate magnetic shields of high performance, particularly for quasi-static and low-frequency fields. These largely rely on the magnetic properties of the shielding material. Magnetic shaking can enhance the material's permeability by reducing hysteresis loss, though this method introduces field interference into the shielding device, complicating the magnetic environment. In this study, an attenuation coefficient is introduced into the Jiles-Atherton model to quantify the suppression effect of magnetic shaking on hysteresis loss, based on measurements of magnetic properties under the shaking fields. To improve shielding performance while minimizing additional interference, the frequency of magnetic shaking is increased and applied only to the outermost layer of the shielding device. Through testing and fitting results, the impact of various magnetic shaking conditions on a cubic magnetic shielding device is examined. By applying a shaking field of 200 Hz solely to the outermost layer, the shielding factor (@0.01 Hz) of a three-layer device increases by 77.4% without additional magnetic noise. This method is also applied to a magnetically shielded room, enhancing its shielding factors by more than two times.