短路微带线法测量微波铁氧体铁磁共振线宽ΔH_ω

Ferromagnetic resonance linewidth ΔH_ω measurement of microwave ferrite by shorted microstrip method

基于传输线理论提出了宽频带测量微波铁氧体铁磁共振线宽的短路微带线法。通过有效参数模型,分析放入样品前后短路微带线单端口网络反射系数S11的变化,进而得到铁磁共振线宽ΔH_ω=Δω/γ,其中Δω为磁导率虚部共振峰的半高宽。设计和制作了短路微带线夹具,并利用所设计的微带夹具测量了钇铁石榴石(YIG)材料的ΔH_ω。最后分析了退磁因子对共振频率的影响,并讨论了样品表面缺陷对ΔH_ω的影响。该方法不仅测量准确度高,操作简单,更解决了低频测量铁磁共振线宽的难点。

A broadband shorted microstrip line measurement method of ferromagnetic resonance （FMR） linewidth △Hω for microwave ferrite is proposed based on transmission line theory. Different from conventional △H derived from field width, △Hω is obtained by sweeping frequency. The effective parameter model is utilized to analyze the changes of the reflection coefficient Sn of microstrip line with and without a sample. By the method mentioned above, the △Hω=△ω/γ is obtained, where △ω is the full-width at half-maximum （FWHM） for the peak in the imaginary part of complex permeability at resonance. Using the designed test fixture, △Hω of yttrium iron garnet （YIG） material is reported. The effect of thedemagnetizing factors at the resonance frequency is investigated. Meanwhile, the impact of the sample surface imperfections on △Hω is discussed. Compared to the conventional method, this method is easily operated with high accuracy and the disadvantages of linewidth measurement at low frequency are overcome.