[论文解读] Ferromagnetic Wires Composite Media with Tunable Scattering Spectra at Microwaves

D. P. Makhnovskiy, Л. В. Панина+3 more|arXiv (Cornell University)|Feb 27, 2006

Electromagnetic wave absorption materials参考文献 2被引用 76

一句话总结

本文展示了基于铁磁性导线的复合介质，可通过外加磁场或机械应力实现可调谐的微波散射谱。通过利用CoFeCrSiB玻璃包覆非晶态导线的磁阻抗响应，作者在仅施加1–3 Oe磁场或0.1 MPa应力的情况下，实现了高达10 dB的透射谱调制，实验验证了1–8 GHz频段内的理论预测。

ABSTRACT

We demonstrate composite media with ferromagnetic wires that exhibit a frequency region at the microwave regime with scattering spectra strongly dependent on an external magnetic field or stress. These tunable composite materials have recently been proposed theoretically; however, no direct experimental verification has been reported. We used composite materials with predominantly oriented CoFeCrSiB glass-coated amorphous wires having large magnetoimpedance at GHz frequencies. The free space measurements of reflection and transmission coefficients were conducted in the frequency range 1-8 GHz in the presence of an external static magnetic field or stress applied to the whole sample. In general, the transmission spectra show greater changes in the range of 10dB for a relatively small magnetic field of few Oe or stress of 0.1 MPa. The obtained results are quantitatively consistent with the analytical expressions predicted by the effective medium arguments. The incident electromagnetic wave induces an electrical dipole moment in each wire, the aggregate of which forms the effective dipole response of the whole composite structure in the radiative near or far field region. The field and stress dependences of the effective response arise from a field or tensile stress sensitivity of the ac surface impedance of a ferromagnetic wire. In the vicinity of the antenna resonance the variations in the magneto-impedance of the wire inclusions result in large changes of the total effective response. A number of applications of proposed materials is discussed including the field tunable microwave surfaces and the self-sensing media for the remote non-destructive evaluation of structural materials.

研究动机与目标

• 通过实验验证铁磁性导线复合材料中可调谐微波散射的理论预测。
• 研究外加磁场和机械应力对导线基复合材料电磁响应的影响。
• 展示利用非晶态导线中的磁阻抗实现微波透射与反射谱动态调控的可行性。
• 探索该技术在场控可调谐微波表面及结构材料无损检测中的潜在应用。

提出的方法

• 采用主要取向的CoFeCrSiB玻璃包覆非晶态导线制备复合介质，其在GHz频段具有高磁阻抗特性。
• 在1–8 GHz频率范围内，施加静态磁场或单轴应力，对反射系数和透射系数进行自由空间测量。
• 基于单个导线弥散体作为谐振天线的集体响应，分析复合结构的有效偶极响应。
• 将有效响应的磁场与应力依赖性归因于铁磁性导线交流表面阻抗的变化，该变化由磁阻抗调制引起。
• 利用有效介质理论推导的解析表达式，与实验数据进行定量比较。
• 在近场与远场区域均进行测量，以评估复合系统的辐射响应特性。

实验结果

研究问题

• RQ1 在施加磁场或应力的条件下，铁磁性导线复合材料能否表现出外部可调谐的微波散射谱？
• RQ2 单个导线的磁阻抗如何影响复合材料在微波频段的有效电磁响应？
• RQ3 在小磁场或低机械应力下，透射与反射谱的调制程度有多大？
• RQ4 观察到的可调谐性是否与有效介质理论预测的定量结果一致？
• RQ5 该可调谐响应在微波器件设计与无损检测中的实际意义是什么？

主要发现

• 在仅1–3 Oe的较小磁场作用下，复合介质的透射谱变化最大可达10 dB。
• 仅0.1 MPa的应力即可引起可测量的散射谱变化，表明对机械形变具有极高灵敏度。
• 观察到的可调谐性与铁磁性导线交流表面阻抗的磁场与应力依赖性密切相关。
• 实验结果与基于有效介质理论推导的解析表达式表现出极佳的定量一致性。
• 复合结构的有效偶极响应主要由导线弥散体在微波频段作为谐振天线的集体行为所主导。
• 研究结果支持利用此类复合材料实现场控可调谐微波表面及用于结构健康监测的自感应材料的可行性。