Magnetism

In this paper, a sharp band-pass filter (BPF) with enhanced pass-band and stop-band specifications is presented. The filter can be utilized for 5G mid-band applications along with LTE42 (3.4–3.6 GHz) and LTE43 (3.6–3.8 GHz) to comply with the standards of different countries. The initial design of the filter consists of a high impedance transmission line connecting the filter’s two ports, which are terminated by 50 Ω resistors. Although this design results in reasonable pass-band characteristics, its stop-band and transition-band characteristics are relatively weak. Due to this shortcoming, the stop-band and transition-band characteristics of the filter are improved by locating sharp transmission zeros within the stop-band to determine the filter bandwidth and to significantly increase the stop-band attenuation. These modifications are achieved by inserting a pair of shunt short- and open-circuit stubs, a pair of short-circuited U-shaped parasitic elements, and a central short-circuited U-shaped element. The filter is mathematically analyzed and modeled, and the design steps are also demonstrated. The simulation and measured results are compatible, and the measurements show an insertion loss of 0.35 dB, stop-band attenuation larger than 20 dB, sharp transmission zeros, and a transition-band value within 10% of the center frequency.

Soft magnetic materials determine the efficiency, size, thermal burden, and reliability of transformers, inductors, electrical machines, electromagnetic interference (EMI) components, and magnetic sensors. This review differs from property-by-property surveys by using a condition-aware, application-driven framework: magnetic performance is compared only together with frequency, peak magnetic flux density, temperature, waveform, direct current (DC) bias, geometry, and processing route. After a concise treatment of coercivity, permeability, saturation polarization, magnetostriction, and loss mechanisms, the major material families are quantitatively compared in terms of magnetic performance, processing, cost, and industrial maturity. The review then maps these families onto grid transformers, high-speed electrical machines, wide-bandgap power converters, integrated magnetics, wireless power transfer, aerospace electrical systems, and radiofrequency components. Particular attention is given to the trade-offs among saturation polarization, permeability, core loss, mechanical strength, thermal stability, manufacturability, and sustainability. Recent advances in strong and ductile soft magnets, wide-temperature ferrites, vortex and easy-plane composites, mixed-powder soft magnetic composites, nanocrystalline flake-ribbon cores, and additive manufacturing are assessed by technology maturity. A prioritized roadmap identifies near-term needs for standardized condition-specific data and manufacturing control, medium-term opportunities in magnetic–thermal co-design and digital twins, and longer-term prospects for adaptive, self-healing, and GHz magnetic architectures. The resulting framework is intended to support both material development and defensible industrial material selection.

The static and dynamic magnetic responses of symmetric Fe/Al/Fe trilayers were investigated as a function of the thickness of the nonmagnetic spacer layer thickness, with t_Al ranging from 0 to 2 nm. Samples showed ferromagnetic coupling between Fe layers for all values of t_Al, despite presenting characteristics of low-quality thin films, including high roughness and low-saturation magnetic moments. However, it was demonstrated that inclusion of a thin nonmagnetic Al spacer is an effective method to reduce the effective apparent damping parameter (α_app) of the dominant acoustic mode of the multilayered system. Specifically, α_app was reduced from 0.030 to 0.013 when the Al spacer thickness exceeded the characteristic roughness of the layers (t_Al ≥ 1.4 nm). This reduction coincided with the appearance of distinct acoustic and optical resonance modes, indicating a transition from a direct exchange-coupled regime dominated by pinholes to a regime dominated by dipolar coupling. This suggests that decoupling the ferromagnetic layers is a viable strategy for developing low-damping Fe-based materials, even in systems with significant structural imperfections.