Magnetic-field induced vertically oriented structure engineering for significantly enhanced electromagnetic absorption
Kaiyuan Fan, Huazhi Gu, Chenghao Wang, Huimin Zhou, Siyuan Dong, Wenqi Zhao, Yousi Chen, Xigao Jian, Cheng Liu
Abstract
Magnetic chains impart composites with excellent low-frequency electromagnetic absorption (EMA) performance for 5G applications, however, it remains a challenge to further enhance EMA performance at lower filler contents through structural design. Therefore, a vertically oriented structure of FeCo chains in a polydimethylsiloxane (PDMS) matrix is initially fabricated through a magnetically induced hot-pressing method. FeCo possesses the highest saturation magnetization (238.67 emu·g⁻1, compared to 105 emu·g⁻1 of the widely used CoNi) and superior permeability among other ferromagnetic chains. The composite exhibits a minimum reflection loss of -46.8 dB and a maximum bandwidth of 6.20 GHz at 1.2 mm, fully encompassing the Ku band. The oriented composites exhibit significantly broader bandwidths at thinner thicknesses, with 1.2 GHz at 3.8 mm and 1.96 GHz at 2.8 mm, compared to 0.85 GHz at 4.3 mm and 1.45 GHz at 3.2 mm of unoriented counterparts, covering n77, n78, and n79 bands in 5G communication, respectively. Moreover, the mechanism of property enhancement from the orientation design is thoroughly investigated. Additionally, oriented composites demonstrate a remarkably enhanced inter-plane thermal conductivity (1.06 W·m⁻1·K⁻1), representing 174% and 790% of that of unoriented configurations (0.61 W·m⁻1·K⁻1) and pure PDMS (0.134 W·m⁻1·K⁻1), respectively. This work provides theoretical and practical guidance on vertically structural engineering for boosting EMA and multifunction to promote the application for next-generation electronic devices. • For the first time, the vertically oriented structure of FeCo chains in polydimethylsiloxane (PDMS) matrix is fabricated through a magnetically induced hot-pressing method. • The oriented designed composites exhibit significantly enhanced electromagnetic absorption and inter-plane thermal conductivity, with a 'sluice' model revealing the properties augment mechanism, as evidenced by HFSS simulation. • FeCo ferromagnetic chains possess higher saturation magnetization and permeability than the widely used CoNi ferromagnetic chains.