Thermosetting organic resins are widely applied as insulating coatings for soft magnetic powder cores (SMPCs) because of their high electrical resistivity. However, their poor thermal stability and thermal decomposition lead to a decrease in electrical resistivity, thus limiting the annealing temperature of SMPCs. The large amount of internal stress generated by soft magnetic composites during pressing must be mitigated at high temperatures; therefore, it is especially important to find organic resins with excellent thermal stabilities. In this study, we prepared SMPCs using poly-silicon-containing arylacetylene resin, an organic resin resistant to high temperatures, as an insulating layer. With 2 wt % PSA as an insulating layer and annealed at 700 °C for 1 h, the FeSiAl SMPCs achieved the best magnetic properties, including the lowest core loss of 184 mW/cm³ (measured at 0.1 T and 50 kHz) and highest permeability of 96.

Soft-magnetic fibers (SMFs) play a crucial role in energy conversion, transmission, and storage within electronic devices. However, conventional SMFs have poor plasticity and are therefore difficult to withstand long-term tensile, torsional, and shear deformation. A high fraction of grain boundaries could improve plastic deformability of conventional SMFs, but deteriorates the coercivity. This severely limits their applications in flexible electronics and multifunctional components. Herein, we propose a strategy to overcome this dilemma, which is realized by coarsening the grains of a Fe₃₄Co₂₉Ni₂₉Al₃Ta₃Si₂ high entropy alloy (HEA) fiber containing ordered coherent nanoprecipitates with small lattice misfit via a simple one-step in-rotating-water spinning method. This allows to reduce domain wall pinning and improve dislocation mobility. The resultant micron-diameter soft-magnetic HEA fiber has a tensile strength of 674 MPa at 23% elongation, a low coercivity of 8.1 Oe, a moderate magnetization of 116 emu/g at 10 kOe and a high Curie temperature of 770 K.

The effect of different particle size distribution of Fe-6.5 wt%Si powder on the microstructure and soft magnetic properties of the corresponding soft magnetic powder cores (SMPCs) was investigated. By optimizing particle size distribution, the density of SMPCs increased and the total core loss significantly decreased. According to the result of loss separation, density of SMPCs is inversely proportional to hysteresis loss, while with increasing the content of the fine particles, the eddy current loss significantly decreased. It was found that with magnetic powder of particle size-grading as 10%, 10%, 60%, and 20% for particles with size between −75 to +38, −38 to +23, −23 to +13, and −13 μm, respectively, the Fe-6.5 wt%Si SMPCs exhibit optimal comprehensive magnetic performances with the effective permeability of about 60, the percent permeability at 100 Oe is up to 70%, and the lowest core loss of 553 mW/cm³.

Nowadays, in view of the increasingly serious problems of electromagnetic interference (EMI) and radiation pollution, smart EMI shielding materials with tunable shielding effectiveness (SE), especially “On/Off” switchable capability, are highly desirable. Herein, Co‐based amorphous wires (AWs) with excellent soft magnetic and mechanical properties are regularly arranged on a 3D‐printed mold as tunable EMI shielding composites. The EMI SE can be easily tuned in the range of ≈0.6–24.7 dB by way of rotation, which has been confirmed to be an effective way to achieve free tuning of EMI SE by simulation. In addition, by compositing AWs with reduced graphene oxide and constructing a double‐layer structure with a gap of 1/4 wavelength in the X‐band, a much wider SE tuning range of ≈1.0–57.7 dB is further realized. The representative “On/Off” switchable shielding capability that can switch between EM transmission and effective shielding, together with the wide SE tuning range larger than 50 dB, shows the great potential of Co‐based AW composites in smart EMI shielding applications.