Excellent dielectric response and microwave absorption in magnetic field-induced magnetic ordered structures

Weak interactions prevent the magnetic particles from achieving excellent electromagnetic wave absorption (EMA) at a low filler loading (FL). The construction of one-dimensional magnetic metal fibers (1D-MMFs) contributes to the formation of an electromagnetic (EM) coupling network, enhancing EM properties at a low FL. However, precisely controlling the length of 1D-MMFs to regulate permittivity at low FL poses a challenge. Herein, a novel magnetic field-assisted growth strategy was used to fabricate Co-based fibers with adjustable permittivity and aspect ratios. With a variety of FL changes, centimeter-level Co long fibers (Co-lf) consistently exhibited higher permittivity than Co particles and Co short fibers due to the enhancement of the effective EM coupling. The Co-lf exhibits excellent EMA performance (-54.85 dB, 5.8 GHz) at 10 wt.% FL. Meanwhile, heterogeneous interfaces were introduced to increase the interfacial polarization through a fine phosphorylation design, resulting in elevated EMA performances (-51.50 dB, 6.6 GHz) at 10 wt.% FL for Co2P/Co long fibers. This study improves the orderliness of the particle arrangement by regulating the length of 1D-MMFs, which affects the behavior of electrons inside the fibers, providing a new perspective for improving the EMA properties of magnetic materials at a low FL.