Magnetic–Dielectric Synergy in One-Dimensional Metal Heterostructures for Enhanced Low-Frequency Microwave Absorption

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 (RL_min) 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 RL_min 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.