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Development of high-performance magnetic ferrite

Hard magnetic ferrite with gigantic coercivity and high frequency millimeter wave rotation


Graduate School of Science / Faculty of Science

Professor Shin-ichi Ohkoshi (Department of Chemistry, School of Science, the University of Tokyo) and his group have developed a high-performance magnetic ferrite, which exhibits the largest coercivity among metal-oxide-based magnets and the highest frequency electromagnetic wave absorption.

Hard magnetic ferrite with gigantic coercivity and high frequency millimeter wave rotation, rhodium-substituted ε-Fe2O3 (ε-RhxFe2-xO3) © Shin-ichi Ohkoshi

The research group has synthesized a novel ferrite magnet, rhodium-substituted ε-Fe2O3 (ε-RhxFe2-xO3) nanomagnets, by a nanoscale chemical synthesis. The present material recorded a coercive field of 31 kOe (kilo-oersted), which is the largest value among metal-oxide-based magnets and is comparable to those of rare-earth magnets. In addition, ε-Rh0.14Fe1.86O3 exhibits a rotation of the polarization plane of the propagated millimeter wave at 220 gigahertz (GHz, 109 hertz), which is one of the promising carrier frequencies for wireless communications due to its high transmittance of air (the window of air).

The present magnetic ferrite has potential in future high-density magnetic recording media due to its gigantic coercivity. The present material should be useful for high frequency millimeter wave absorbers and rotators (isolators or circulators) as it should restrict electromagnetic interference problems.

This research was published in Nature Communications on September 4th, 2012.

Department release/press release (Japanese)


Asuka Namai, Marie Yoshikiyo, Kana Yamada, Shunsuke Sakurai, Takashi Goto, Takayuki Yoshida, Tatsuro Miyazaki, Makoto Nakajima, Tohru Suemoto, Hiroko Tokoro, Shin-ichi Ohkoshi,
“Hard magnetic ferrite with a gigantic coercivity and high frequency millimetre wave rotation”,
Nature Communications 2012/9/4 (Japan time), doi:10.1038/ncomms2038
Article link


Graduate School of Science

Department of Chemistry

Ohkoshi Laboratory

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