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1. Broadband and Tunable Microwave Absorption Properties from Large Magnetic Loss in Ni–Zn Ferrite

   https://doi.org/10.1002/admt.202301857  

   Ghosh, Subrata; Sharma, Shweta; Li, Wenjie; Nozariasbmarz, Amin; Raman, Lavanya; Liu, Na; Goyal, Gagan K.; Zhang, Yu; Perini, Steven E.; Lanagan, Michael; et al (January 2024, Advanced Materials Technologies)

   Abstract Highly effective electromagnetic (EM) wave absorber materials with strong reflection loss (RL) and a wide absorption bandwidth (EBW) in gigahertz (GHz) frequencies are crucial for advanced wireless applications and portable electronics. Traditional microwave absorbers lack magnetic loss and struggle with impedance matching, while ferrites are stable, exhibit excellent magnetic and dielectric losses, and offer better impedance matching. However, achieving the desired EBW in ferrites remains a challenge, necessitating further composition design. In this study, impedance matching is successfully enhanced and EBW in Ni–Zn ferrite is broadened by successive doping with Mn and Co , without incorporation of any polymer filler. It is found that Ni_0.4Co_0.1Zn_0.5Fe_1.9Mn_0.1O₄material exhibits exceptional EM wave absorption, with a maximum RL of −48.7 dB. It also featured a significant EBW of 10.8 GHz, maintaining a 90% absorption rate (RL < −10 dB) for a thickness of 4.5 mm. These outstanding properties result from substantial magnetic losses and favorable impedance matching. These findings represent a significant step forward in the development of microwave absorber materials, addressing EM wave pollution concerns within GHz frequencies, including the frequency band used in popular 5G technology. 

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2. Application of Artificial Material in Microwave Absorber

   https://doi.org/10.1109/SOUTHEASTCON45413.2021.9401887  

   Saha, Arun K.; Pendleton, Walker G. (April 2021, IEEE SoutheastCon 2021)

   A microwave absorber is designed with a given absorbing material whose relative permittivity and permeability are known. In this design process, impedance matching between absorber and free space is achieved by circular metal patches of predesigned shape printed periodically on absorbing material. Designed microwave absorber along with predesigned designed metal strip is modeled in 3D electromagnetic simulation software HFSS. Simulated frequency response of reflection coefficient verifies impedance matching and absorption at design frequency. 

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3. Inverse designed aperiodic multilayer perfect absorbers for mid infrared enable tunability switchability and angular robustness

   https://doi.org/10.1038/s41598-025-99995-6  

   Nazari, Masoumeh; Banad, Yaser M; Sharif, Sarah (December 2025, Scientific Reports)

   We present a class of inverse-designed, aperiodic multilayer graphene-based perfect absorbers operating in the mid-infrared spectrum (3–5 μm), a range vital for atmospheric transparency and advanced sensing. Our design leverages a fixed material sequence—graphene, PPSU dielectric spacers, and PbSe layers on a gold substrate—while achieving precise spectral tunability solely through layer thickness variation, enabling absorption peak control in 0.25 μm steps without any change in material composition. This physical tunability allows scalable fabrication of wavelength-specific devices using a single manufacturing process. We further demonstrate electrical switchability by dynamically modulating graphene’s chemical potential (µc from 0 eV to 1 eV), enabling absorption amplitude control and wavelength redshifting without structural alteration. The proposed absorber achieves > 99.9% efficiency using only five graphene layers in a compact ~ 2 μm stack, offering significant advantages in size, weight, power, and cost. Our hybrid micro-genetic inverse design algorithm enables this performance while preserving > 90% absorption at incidence angles up to 52°, supporting broad angular robustness. Extensive simulation and field distribution analyses confirm the role of plasmonic confinement and impedance matching. Additionally, we validate the design’s fabrication tolerance and benchmark its performance against recent state-of-the-art absorbers. By combining advanced inverse design with nanophotonic structures, our work advances the field of mid-infrared absorbers, providing a scalable and efficient platform for next-generation optical devices. 

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4. Broadband impedance matching for lossy magnetic metamaterials in conductive media

   https://doi.org/10.1038/s41598-025-11452-6  

   Jenkins, Connor; Kiourti, Asimina (July 2025, Scientific Reports)

   Abstract We present a broadband impedance matching model for traveling waves on lossy magnetic metamaterials known as magnetoinductive waveguides (MIWs) in conductive media. Thus far, broadband impedance matching has only been demonstrated in the case of a lossless MIW in free-space due to complexities introduced by losses and eddy current effects. As such, current studies in conductive environments have been limited to utilizing narrow-band matching techniques or relying on attenuation to mitigate reflections, thus limiting the system performance in terms of bandwidth and transmission loss. The proposed model overcomes these limitations by utilizing the nearest neighbor coupling and binomial approximations to generate transducer design criteria in terms of equivalent circuit parameters for broadband impedance matching. To validate the model, a transducer is designed for a 40-MHz lossy MIW submerged in an ocean water phantom. Reflection coefficient results demonstrate a 15.5% fractional bandwidth and a maximum value of − 9.0 dB in the propagation band of the MIW, indicating excellent performance. This model expands the potential design space of MIWs to include complex environments such as underwater, underground, or on the human body. 

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5. A compact wideband dielectric resonator antenna with optimized inhomogeneous material distribution

   https://doi.org/10.1049/ell2.70107  

   Bellundagi, Trupti; Yang, Binbin (December 2024, Electronics Letters)

   This article proposes a novel compact wideband dielectric resonator antenna design that incorporates inhomogeneous material distribution in a cubic structure. Specifically, in this design, the cubic dielectric resonator antenna is divided into multiple small blocks, and a continuous genetic algorithm is employed to optimize the material property of each block in order to maximize the radiation bandwidth. As a result, a cubic dielectric resonator antenna with inhomogeneous material distributions is designed and tested. In measurement, the proposed compact dielectric resonator antenna design exhibits 64.9% impedance bandwidth (4.08–8 GHz), considerably higher than the bandwidth of the initial homogeneous dielectric resonator antenna. The maximum system gain achieved over the frequency range is 9 dB at 7 GHz, with a peak measured system efficiency of 90.6%. 

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