The ever-increasing electromagnetic (EM) wave bands employed in electronic devices and detection radars have spawn an urgent demand for advanced EM wave absorbers with wideband dissipation capabilities to mitigate EM interference and radiation. A range of material species have been investigated as absorbers, encompassing alloys and carbon materials, etc. Magnetic materials including soft magnetic alloys and ferrites are regarded as promising candidates due to their abundant loss mechanisms involving conductive/dielectric and magnetic attenuation. Among them, magnetic alloys such as FeCo stands out due to their high saturation magnetization and permeability. Nevertheless, the large electrical conductivity of magnetic alloys may lead to poor impedance matching, meanwhile the Snoek’s limit inherently restricts permeability and magnetic resonance, which ultimately impedes their attenuation capability in the high-frequency band.
Integrating FeCo alloys with insulating materials provides an effective strategy to optimize impedance matching. The isolating effect of low-conductivity materials enables spatial separation of FeCo particles, thereby suppressing severe aggregation and excessive conductivity. However, nonmagnetic components in such composite systems often trigger magnetic dilution, resulting in reduced permeability and deteriorated magnetic loss. Furthermore, conventional methods for composite fabrication hinder precise control over the size and dispersity of FeCo particles, resulting in difficulty to achieve single-domain magnetic particles for strong anisotropy and high-frequency magnetic loss. Consequently, rational design of FeCo composite absorbers with exceptional impedance matching and strong dissipation ability remains challenging.
In this work, hollow FeCo magnetoelectric composite nanocages have been fabricated via etching and thermal reduction of FeCo-based PBA. The in-situ preparation allows confinement between the FeCo and the CoFe 2 O 4 phase. On one hand, well-dispersed FeCo nanoparticles with quasi-single-domain size have been obtained, giving rise to enhanced surface anisotropy and natural resonance. On the other hand, the formation of ferrimagnetic CoFe 2 O 4 phase mitigates magnetic dilution and provides abundant heterointerfaces for improved polarization loss and impedance matching . As such the FeCo magnetoelectric composite exhibits excellent EM wave absorption with minimum reflection loss (RL) of -47.4 dB and broad effective absorption bandwidth (EAB, RL < -10 dB) of 7.10 GHz at a small thickness of 1.9 mm. This work not only demonstrates the superior EM wave absorption performance of FeCo magnetoelectric composite nanocages, but also offers insights for the rational design of magnetic composite materials for diverse EM functional applications.
D OI Link:
https://doi.org/10.26599/NR.2026.94908356
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Nano Research is a peer-reviewed, open access, international and interdisciplinary research journal, sponsored by Tsinghua University and the Chinese Chemical Society, published by Tsinghua University Press on the platform SciOpen. It publishes original high-quality research and significant review articles on all aspects of nanoscience and nanotechnology, ranging from basic aspects of the science of nanoscale materials to practical applications of such materials. After 18 years of development, it has become one of the most influential academic journals in the nano field. Nano Research has published more than 1,000 papers every year from 2022, with its cumulative count surpassing 8,000 articles. In 2025 InCites Journal Citation Reports, its 2025 IF is 9.4 (8.3, 5 years), and it continues to be the Q1 area among the four subject classifications. Nano Research Award, established by Nano Research together with TUP and Springer Nature in 2013, and Nano Research Young Innovators (NR45) Awards, established by Nano Research in 2018, have become international academic awards with global influence.
Nano Research
Confinement Engineering of FeCo Magnetoelectric Composite Nanocages for Enhanced Magnetic Loss and Wideband Electromagnetic Wave Absorption
29-Apr-2026