Theoretical Design of a High-Frequency Millimeter Wave Absorbing Sheet Composed of Gallium Substituted -Fe O Nanomagnet

摘要

To inhibit electromagnetic interference problems in next generation wireless communications using millimeter waves, the development of millimeter wave absorbers is crucial. Herein we theoretically designed a millimeter wave absorbing sheet composed of $varepsilon$-Ga $_{x}$Fe $_{2-x}$O $_{3}$ nanomagnets based on impedance matching calculations. From the previously reported magnetic permeability $(mu)$ of $varepsilon$-Ga$_{x}$Fe$_{2-x}$O$_{3}$, the artificial frequency dependences of the real $(mu^{prime})$ and imaginary parts $(mu^{primeprime})$ were constructed using the Landau-Lifshitz equation. The impedance matching calculation showed that a 217.2 $mu$m thick metal-backed $varepsilon$-Ga $_{0.537}$Fe $_{1.463}$O $_{3}$ sheet perfectly absorbs 60 GHz millimeter wave, while a 201–233 $mu$m thick sheet can absorb 99% of the millimeter wave,- i.e., a reflectance loss (RL) of ${-}20$ dB. The frequency dependence of RL indicated that the frequency range where RL exceeds ${-}20$ dB is as broad as 1 GHz (59.5–60.5 GHz). Such theoretical calculations will be useful for fabricating a 60 GHz-band millimeter wave absorber sheet from the viewpoint of industrial applications.