A three-stage demagnetization method based on quantified irreversible permeability and a dynamic hysteresis parameter Jiles–Atherton model

High performance magnetic shielding is necessary in the fields of high-precision measurement based on quantum sensors such as biological magnetic field. Demagnetization is one of the most prevalent techniques employed to enhance the performance of a magnetically shielded room (MSR). This paper proposes a three-stage demagnetization method based on the quantification of incremental irreversible permeability and the dynamic hysteresis parameter JA(DHP-JA) model. The method is developed from the fundamental perspective of demagnetization theory. First, a quantitative indicator is introduced to characterize the irreversible magnetization, which is the primary target in demagnetization. Second, the dynamic variation of hysteresis parameters with magnetization state is realized through a combination of physical formula derivation and parameter fitting. Finally, by integrating the irreversible magnetization indicator with the DHP-JA model, the three-stage demagnetization method is applied to MSRs, achieving an optimized time distribution among the three stages. As a result, the residual field at the center of a single-layer box-type MSR with dimensions of 420 mm × 420 mm × 420 mm and 2 mm thickness is reduced to 0.4 nT, representing a 58% reduction compared with the conventional optimal method. For a more complex tooth-type MSR, the proposed three-stage demagnetization method reduces the central residual field by 31.3% relative to the conventional approach.