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Issue 34, 2013
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The synthesis of rhodium substituted ε-iron oxide exhibiting super high frequency natural resonance

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Abstract

In this study, we demonstrate a synthesis of rhodium substituted ε-iron oxide, ε-RhxFe2−xO3 (0 ≤ x ≤ 0.19), nanoparticles in silica. The synthesis features a sol–gel method to coat the metal hydroxide sol containing Fe3+ and Rh3+ ions with a silica sol via hydrolysis of alkoxysilane to form a composite gel. The obtained samples are barrel-shaped nanoparticles with average long- and short-axial lengths of approximately 30 nm and 20 nm, respectively. The crystallographic structure study using X-ray diffraction shows that ε-RhxFe2−xO3 has an orthorhombic crystal structure in the Pna21 space group. Among the four non-equivalent substitution sites (A–D sites), Rh3+ ions mainly substitute into the C sites. The formation mechanism of ε-RhxFe2−xO3 nanoparticles is considered to be that the large surface area of the nanoparticles increases the contribution from the surface energy to Gibbs free energy, resulting in a different phase, ε-phase, becoming the most stable phase compared to that of bulk or single crystal. The measured electromagnetic wave absorption characteristics due to natural resonance (zero-field ferromagnetic resonance) using terahertz time domain spectroscopy reveal that the natural resonance frequency shifts from 182 GHz (ε-Fe2O3) to 222 GHz (ε-Rh0.19Fe1.81O3) upon rhodium substitution. This is the highest natural resonance frequency of a magnetic material, and is attributed to the large magnetic anisotropy due to rhodium substitution. The estimated coercive field for ε-Rh0.19Fe1.81O3 is as large as 28 kOe.

Graphical abstract: The synthesis of rhodium substituted ε-iron oxide exhibiting super high frequency natural resonance

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Publication details

The article was received on 29 Apr 2013, accepted on 01 Jul 2013 and first published on 17 Jul 2013


Article type: Paper
DOI: 10.1039/C3TC30805G
Citation: J. Mater. Chem. C, 2013,1, 5200-5206
  • Open access: Creative Commons BY-NC license
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    The synthesis of rhodium substituted ε-iron oxide exhibiting super high frequency natural resonance

    A. Namai, M. Yoshikiyo, S. Umeda, T. Yoshida, T. Miyazaki, M. Nakajima, K. Yamaguchi, T. Suemoto and S. Ohkoshi, J. Mater. Chem. C, 2013, 1, 5200
    DOI: 10.1039/C3TC30805G

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