Key Takeaways & Executive Findings
- •• The hierarchical CoNi@SnO2@Sn heterostructure achieves a minimum reflection loss of −62.29 dB and an effective absorption bandwidth of 2.2 GHz, fully covering the C-band at a thin thickness of 2.61 mm. • The magnetic–dielectric synergy, enabled by CoNi nanosheets and Sn/SnO2 interfaces, enhances impedance matching and attenuation, overcoming the low-frequency absorption bottleneck. • The CNS/TPU composite film exhibits superior low-frequency microwave absorption (RLmin of −61.04 dB, EAB of 2.5 GHz) and improved thermal conductivity (2.41 W m−1 K−1 in-plane), making it suitable for flexible electronics. • This work provides a novel strategy for designing 1D metal-based absorbers with strong magnetic–dielectric synergy, advancing applications in 5G communications and EMI shielding.
Abstract
Microwave absorption (MA) materials often face poor synergy between impedance matching and attenuation in the low-frequency range. Balancing permittivity and permeability through magnetic–dielectric synergy is a promising strategy to address this issue. To realize the synergy, herein, Sn whiskers with an in situ oxide layer served as substrates for magnetic-loss-active CoNi nanosheet growth, forming a hierarchical CoNi@SnO2@Sn (CNS) heterostructure. The CNS absorber achieves a minimum reflection loss (RLmin) value of −62.29 dB with an effective absorption bandwidth (EAB) of 2.2 GHz, covering the entire C-band with 70% absorption at only 2.61 mm thickness. The nanosheet design of CoNi enhances magnetic anisotropy to promote natural resonance, while the conductive Sn core and abundant Sn/SnO2 and CoNi/SnO2 heterointerfaces facilitate conduction loss and dielectric polarization. When composited into a thermoplastic polyurethane (TPU) matrix, the resulting CNS/TPU-2 film (20 wt% CNS) exhibits an RLmin value of -61.04 dB and a 2.5 GHz EAB. Its in-plane and through-plane thermal conductivities reach 2.41 and 0.51 W m−1 K−1, representing 4.1 and 2.6 times those of pure TPU films, respectively, facilitating heat dissipation from protected devices. This work provides valuable insights into magnetic–dielectric synergy for low-frequency MA of 1D metal-based materials, offering promising potential for 5G communications and flexible electronics.
1. Introduction
The rapid advancement of 5G communication technology has significantly accelerated the development of mobile internet [1, 2]. However, it has also intensified electromagnetic interference (EMI) and radiation pollution within 5G-specific frequency bands, particularly in the S-band (2–4 GHz), C-band (4–8 GHz), and sub-bands such as n77 (3.3–4.2 GHz), n78 (3.3–3.8 GHz), and n79 (4.4–5.0 GHz), resulting in signal disruption and equipment malfunction [3–5]. Microwave absorption (MA) materials are capable of attenuating incident electromagnetic waves through mechanisms such as dielectric and magnetic losses, offering effective solutions to EMI and radiation-related issues [6, 7]. Nevertheless, most reported MA materials demonstrate optimal performance in the mid- to high-frequency ranges, primarily in the X-band (8–12 GHz) and Ku-band (12–18 GHz) [8]. For the lower-frequency S- and C-bands, current MA materials often suffer from narrow effective absorption bandwidth (EAB) and require relatively large matching thicknesses [9]. These limitations are mainly ascribed to the weakened synergy between impedance matching and attenuation capability at low frequencies, which is strongly governed by the intrinsic dielectric constant and magnetic permeability of the material [10].
Magnetic metals such as Fe, Co, Ni, and their alloys, which possess high magnetic permeability and moderate dielectric properties, are commonly utilized for low-frequency MA applications [11]. Their unfilled 3d orbitals facilitate the formation of external magnetic moments, enabling microwave attenuation via mechanisms such as eddy current loss and natural resonance. However, the classical Snoek limit imposes a trade-off between magnetic permeability and resonance frequency, restricting these materials’ performance at the higher end of the low-frequency range [12]. Moreover, magnetic loss typically decreases sharply with increasing frequency, and the natural resonance range is relatively narrow. In contrast, dielectric-type absorbers exhibit b
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Feiyue Hu, Peigen Zhang, Pei Ding, Shuo Zhang, Bingbing Fan, Ali Saffar Shamshirgar, Wei Zheng, Wenwen Sun, Longzhu Cai, Haijiao Xie, Qiyue Shao, Johanna Rosen, ZhengMing Sun (2026). Magnetic–Dielectric Synergy in One-Dimensional Metal Heterostructures for Enhanced Low-Frequency Microwave Absorption. Nano-Micro Letters. https://doi.org/10.1007/s40820-025-01995-8
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Frequently Asked Questions
What is the main challenge in low-frequency microwave absorption?
The main challenge is achieving a balance between impedance matching and attenuation capability at low frequencies, which is often limited by the intrinsic dielectric and magnetic properties of materials.
How does the CoNi@SnO2@Sn heterostructure achieve magnetic-dielectric synergy?
The heterostructure combines magnetic CoNi nanosheets with a conductive Sn core and SnO2 interfaces, enhancing magnetic anisotropy for natural resonance and providing conduction loss and dielectric polarization, thus improving impedance matching and attenuation.
What are the key performance metrics of the CNS absorber?
The CNS absorber achieves a minimum reflection loss of −62.29 dB and an effective absorption bandwidth of 2.2 GHz, covering the entire C-band with 70% absorption at a thickness of only 2.61 mm.
What are the potential applications of the CNS/TPU composite film?
The CNS/TPU film exhibits excellent low-frequency microwave absorption and thermal conductivity, making it suitable for flexible electronics, 5G communication devices, and heat dissipation applications.
How does the CNS/TPU film improve thermal management?
The film shows in-plane and through-plane thermal conductivities of 2.41 and 0.51 W m−1 K−1, respectively, which are 4.1 and 2.6 times higher than pure TPU films, facilitating efficient heat dissipation from protected devices.
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