Transverse magnetic annealing of Fe-based nanocrystalline alloys for enhanced soft magnetic properties and magnetic noise suppression in magnetic shielding devices

Fe-based nanocrystalline magnetic shielding devices (MSDs) are capable of providing ultra-weak magnetic environments with high shielding factors (SFs) and low magnetic noise (MN) for biomagnetic signal detection. In this study, Fe₈₂Cu₂Nb₆Si₈B₂ nanocrystalline alloys were treated by transverse magnetic-field annealing (TFA, 400–450 °C, 100 mT) to tailor magnetic anisotropy, and compared with a conventionally annealed reference (ZFA-00). TFA yields improved soft-magnetic performance: the saturation flux density approaches 1 T, the maximum permeability reaches 162100 at 60 mT and 20 Hz, coercivity decreases to 0.0316 A/m, and power loss is reduced to 7.23 × 10⁻⁵ kW/m³ . Microstructural analyses indicate broadly comparable nanocrystalline morphologies, while transverse-field annealing predominantly tailors magnetic behavior via induced in-plane uniaxial anisotropy (K_u/H_k) and low-field magnetization regulation[17]. Further analysis shows that the induced anisotropy energy constant Ku decreases to 1.211 J/m³ under optimal annealing conditions, while a stable transverse uniaxial anisotropy is introduced, yielding an average magnetocrystalline anisotropy energy density 〈K₁〉 of 2.85 × 10² J/m³ . The induced anisotropy effectively suppresses magnetic domain rotation and facilitates domain wall pinning-free motion, thereby realizing the dual optimization of soft-magnetic properties and MN reduction. In composite magnetic shielding device (MSD) prototypes, the device lined with TFA-400 ribbons exhibits a 25–55.9 % reduction in low-frequency MN compared with the ZFA-00-lined counterpart. These results demonstrate that TFA is an effective processing route to low-loss and low-noise nanocrystalline liners for high-performance shielding in ultra-weak magnetic environments.