Optical Properties of Epsilon Iron Oxide Nanoparticles in the Millimeter- and Terahertz-Wave Regions

Epsilon iron oxide (ε-Fe2O3) is attracting global attention as a magnetic material with a large magnetic anisotropy. In this article, the optical properties of ε-Fe2O3 nanoparticles and the metal-substituted series of ε-MxFe2−xO3 (M = Ga, In, and Al) are studied over a wide frequency range from the...

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Bibliographic Details
Published in:Bulletin of the Chemical Society of Japan 2022-03, Vol.95 (3), p.538-552
Main Authors: Tokoro, Hiroko, Nakabayashi, Koji, Nagashima, Shuntaro, Song, Qinyu, Yoshikiyo, Marie, Ohkoshi, Shin-ichi
Format: Article
Language:English
Subjects:
Absorption
Aluminum
Crystal structure
Electronic structure
Far infrared radiation
Ferric oxide
First principles
Frequency ranges
Gallium
Infrared spectroscopy
Iron oxides
Magnetic anisotropy
Magnetic materials
Magnetic properties
Magnons
Masterpiece Materials with Functional Excellence
Mathematical analysis
Millimeter waves
Nanoparticles
Optical properties
Phonons
Resonance
Substitutes
Terahertz frequencies
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Summary:Epsilon iron oxide (ε-Fe2O3) is attracting global attention as a magnetic material with a large magnetic anisotropy. In this article, the optical properties of ε-Fe2O3 nanoparticles and the metal-substituted series of ε-MxFe2−xO3 (M = Ga, In, and Al) are studied over a wide frequency range from the millimeter-wave to terahertz-wave region, 30 GHz–30 THz, using terahertz time-domain, far-infrared, and Raman spectroscopies. To understand the spectroscopic data, first-principles calculations of the electronic structure and phonon modes are performed. First, an ε-Fe2O3 bar magnet is introduced and its atomic movements are calculated by phonon mode calculations. Second, the phonon modes of Ga-substituted ε-Fe2O3 are calculated. Far-IR, mid-IR, and Raman spectroscopies confirm that the calculated and observed spectra show good agreement. Third, the influences of In-substitution on the crystal structure, magnetic properties, and millimeter-wave absorption are described. In high-frequency millimeter-wave absorption due to magnon, the resonance frequency decreased with In-substitution. Finally, the millimeter-wave absorption property of ε-AlxFe2−xO3 is described. An absorption peak due to the natural resonance occurs at 100 GHz. The rotation data of the transmitted millimeter wave are determined by millimeter-wave–polarization-plane measurements.
ISSN:0009-2673
1348-0634
DOI:10.1246/bcsj.20210406