A Millimeter-Wave Tunable Electromagnetic Absorber Based on $varepsilon$ -Al$_{rm x}$ Fe$_{2-{rm x}}$ O$_{3}$ Nanomagnets

摘要

High-performance millimeter-wave absorber composed of $varepsilon$-Al $_{rm x}$Fe $_{2-{rm x}}$O $_{3}$ nanomagnets is prepared by sol-gel techniques. Free space quasi-optical spectrometer equipped with a set of tunable backward-wave oscillators as power sources is used in this work to study the absorption property of this series of materials. Special aluminum-disc sample container with thickness of 2 mm is fabricated. Transmittance spectra of $varepsilon$-Al$_{rm x}$Fe$_{2 - {rm x}}$O$_{3}$ with different x values (${rm x} = $ 0.66 and 0.49) are recorded using our free space spectrometer. Strong magnetic absorption at 95 GHz (corresponding to ${rm x} = $ 0.66) and 105 GHz (${rm x} = $ 0.49) are found. Combining the data obtained in this and previous work, second order polynomial curve is simulated to study the x parameter dependence of absorption frequencies. The simulation results are in good agreement with the experimental ones.