Magneto absorption measurements of nano-size ε-AlxFe2-xO3 powder materials at millimeter wavelengths

Ferromagnetic absorption spectra of epsilon-AlxFe2-xO3 powders with various x parameters and densities were obtained using free space quasi-optical spectrometer. Two absorption peaks located at around 95 and 105 GHz have been found. The 95 GHz absorption corresponds to x parameter value of 0.66; while the 105 GHz absorption corresponds to x-parameter value of 0.49. The absorption peak shifts to the lower frequency with increasing value of x parameter. The change in densities resulted in change in absorption intensity. The absorption characteristics are repeatable for these specimens prepared even at eight months interval. These absorbers are composed of epsilon-AlxFe2-xO3 nanomagnets and 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 transmittance and absorption property of this series of materials at millimeter wave frequencies. The transmittance and absorbance spectra of epsilon-AlxFe2-xO3 powders with different x values (x - 0.66 and 0.49) and densities are recorded using the free space spectrometer. Strong magnetic absorption centering at 95 GHz (corresponding to x - 0.66) and at 105 GHz (x - 0.49) are found for all densities. (C) 2011 American Institute of Physics. [doi:10.1063/1.3554250]