Experimental studies on the performance of magnetic shields under different magnetization conditions

Abstract

In recent decades, magnetic shields have provided basic experimental environments for the measurements of extremely weak magnetic fields represented by the biological magnetic signal. Excellent shielding performances, including the low residual field and high shielding factor, are necessary to ensure the quality of these weak magnetic signals and avoid the interference of external magnetic field. The magnetic shielding performance of the same device can be affected by the different degaussing and test conditions, which remains systematically studied. In this paper, the experiments with variable magnetization conditions, including different degaussing orders, test fields and environmental fields, are established in a nearly zero-field space to simulate the different situations during measurement. The residual field and shielding factor of the cubic shielding device are tested in these cases. Meanwhile, these shielding performances are analyzed from the perspective of the magnetization state and calculated based on the magnetic properties which are tested and fitted by Jiles-Atherton model. The results show the influence of these different conditions on the shielding performances of the cubic device, consistent with the numerical calculation. Under the same environmental field, the different degaussing order and test field lead to completely different residual field and shielding performance, respectively. The influence of the earth magnetic field on the shielding factor can be ignored due to its tiny equivalent bias field determined by the anhysteretic magnetization curve.

Study on the magnetic shielding properties of nanocrystalline strips under bending stress

“…A series of hysteresis models, such as Preisach [16]and J-A(Jiles-Atherton) [6,7,17], have been developed to describe the nonlinear magnetization state of soft ferromagnetic shielding materials. Among them, the J-A hysteresis model has a clear physical meaning, which is constructed by describing the wall movement law of magnetic domains under the pinning-rolling effect, and can accurately describe the nonlinear relationship between the magnetic induction strength and the magnetic field strength [17]. Therefore, the J-A model is adopted in this paper.…”

“…In this paper, the population-based metaheuristic algorithm called the Gazelle Optimization Algorithm (GOA) is used to obtain the initial parameters of the J-A model: a, k, α, c, and M s . To quantitatively analyze the computational accuracy of the model, the RMSE (Root Mean-Square Error) is chosen to measure the degree of model accuracy, and its calculation formula is shown in equation (12) [7,17,28]:…”

Research on the stress magnetic coupling effect of a permalloy based on an optimized Jiles Atherton model in magnetic shielding devices

“…Typical magnetic shielding devices weaken the external magnetic field [11,12] through the magnetic flux shunt effect of permalloy (a kind of high magnetic conductivity material) [13,14]. The magnetic properties of permalloy will determine the shielding performance, such as the relative permeability and coercivity.…”

The SF and remanence evaluation of magnetic shields based on SST for low-frequency and degaussing situation

“…Yang et al has further tested the B-H relationship and studied the corresponding remanence of MSR under the degaussing waveform of various parameters [16]. In the previous research, the magnetic properties are generally tested using a toroidal sample instead of the square permalloy plate of the practical use [17][18][19]. The magnetic characteristics of Mumetal in various physical shapes and dimensions are affected by the different annealing temperatures during the heat treatment process [20][21][22].…”