The rapid development of electronic information technology has led to an increasingly serious problem of electromagnetic interference (EMI), which has driven the rapid development of electromagnetic wave absorption materials. Among these materials, soft magnetic materials have attracted much attention due to their excellent magnetic loss capability arising from their high saturation magnetization. However, the ferromagnetic resonance behavior of soft magnetic materials is hindered by the trade-off between loss capability and frequency, known as the Snoek limit. The traditional method to overcome the Snoek limit is to prepare magnetic/dielectric composites, but this method has limited improvement on the intrinsic ferromagnetic resonance frequency of magnetic materials. Therefore, it is crucial to develop new methods to break through the Snoek limit to promote the research and development of high-frequency magnetic loss materials and optimize the performance of absorbing materials.
Methods
Prof. Xue-Feng Zhang's team from Hangzhou Dianzi University proposed a new strategy to optimize the magnetic loss performance of magnetic Fe3C by regulating its shape anisotropy through solid-state phase transformation. By isothermally quenching eutectoid steel at different temperatures to precipitate Fe3C flakes with different thicknesses and then etching away the ferrite phase via electrochemical dealloying, magnetic Fe3C microflake powders with varying anisotropy were obtained.
Highlights & Significance
Breaking the Snoek Limit: By precisely controlling the shape anisotropy of Fe3C microflakes through solid-state phase transformation, the resonance frequency was effectively tuned from 9.47 GHz to 11.56 GHz, breaking through the limitation of the Snoek limit.
Excellent Absorption Performance: At 11.56 GHz, the imaginary part of the complex permeability reached 0.9, the minimum reflection loss was -52.09 dB (15.85 GHz, 2.90 mm), and the effective absorption bandwidth was 2.55 GHz (1.20 mm, ≤-10 dB), demonstrating excellent microwave absorption performance.
Revealing the Role of Anisotropy: The relationship between anisotropy and high-frequency magnetic loss capability was elucidated, providing new ideas for designing high-performance microwave absorption materials.
Expanding Material Applications: This study realized the functional application of traditional structural materials, providing inspiration for obtaining functional materials from other conventional structural materials.
This study developed a simple, efficient, and controllable method for preparing Fe3C microflakes and significantly enhanced their high-frequency magnetic loss capability and microwave absorption performance by regulating their shape anisotropy through solid-state phase transformation. The research results provide new ideas and strategies for the design of high-performance microwave absorption materials and the functional application of traditional structural materials.
Fig. 2. Magnetic loss abilities. (a) Real part (μ') and (b) imaginary part (μ") of the complex permeability at the frequency regions of 6–14 GHz. Colored fitted lines are fitted from the experimental lines (gray lines) through the Landau–Lifshitz–Gilbert (LLG) equation. (c) Summarization of the natural resonance frequencies, effective absorption bandwidth, reflection loss and the corresponding thickness of Fe3C. (d) Comparison of fr versus μ" of reported soft magnetic materials and Fe3C. (e) The tan δM of Fe3C microflakes in the frequency region of 6–14 GHz.
Authors
R. Zhao, T. Gao, Y. Li, Z. Sun, Z. Zhang, L. Ji, C. Hu, X. Liu, Z. Zhang, X. Zhang, G. Qin, Highly anisotropic Fe3C microflakes constructed by solid-state phase transformation for efficient microwave absorption, Nature Communications 15(1) (2024) 1497. DOI: https://doi.org/10.1038/s41467-024-45815-w
