具有横向磁晶各向异性的钴纳米线的微波吸收性能

使用电化学脉冲沉积法制备了磁晶各向异性易磁化方向(c轴)垂直纳米线长轴方向的钴纳米线.受到磁晶各向异性、静磁相互作用等因素与形状各向异性相互竞争的结果,纳米线阵列的磁滞回线显示出较弱的磁各向异性.此外,在2—18 GHz频率范围内,纳米线/石蜡复合材料的介电色散谱的虚部在5 GHz处有一个主峰,在10 GHz附近有一个较弱的峰;德拜弛豫特性和材料的电导率对这两个峰的形成均有贡献.同时,其磁导率色散谱的虚部在频率为6.1 GHz处有一个主峰,在10 GHz以上有两个较微弱的峰. 前一个峰源于自 关键词： 钴纳米线 介电色散谱 磁导率色散谱 微波吸收剂

Microwave absorbing properties of cobalt nanowires with transverse magnetocrystalline anisotropy

Cobalt nanowires with c-axis perpendicular to the axial direction have been fabricated by the pulsed electrodeposition method. The hysterisis loops of the cobalt nanowire array show little anisotropy due to the competition between shape anisotropy and factors such as magnetocrystalline anisotropy and magnetostatic interaction. The permittivity and permeability dispersion spectra of the nanowire/paraffin composite were measured in the frequency range of 2—18 GHz. It was found that the imaginary part of the permittivity spectra shows a strong peak around 5 GHz and a weak peak around 10 GHz, which are contributed by the Debye relaxation and the conductivity of the nanowires. In the meantime, the imaginary part of the permeability spectra for the nanowire/paraffin composite samples exhibits a strong absorption peak at 6.1 GHz and two minor peaks above 10 GHz. The peak at 6.1 GHz is attributed to the natural resonance mechanism and the other two peaks are duc to eddy current effect. The permeability spectra attributed to natural resonance are fitted using the Landau–Lifshitz–Gilbert equation. Calculation based on the Kittel equation substantiates our fitting results. The electromagnetic wave reflection loss of the nanowire/paraffin composite sample is lower than -20 dB when the thickness of the nanowire/paraffin composite has been adjusted, suggesting that the cobalt nanowire composites can find application as a novel type of microwave absorbers.