Others Nanometer-size hard magnetic ferrite exhibiting high optical-transparency and nonlinear optical-magnetoelectric effect

Ohkoshi, Shin-ichi  ,  Namai, Asuka  ,  Imoto, Kenta  ,  Yoshikiyo, Marie  ,  Tarora, Waka  ,  Nakagawa, Kosuke  ,  Komine, Masaya  ,  Miyamoto, Yasuto  ,  Nasu, Tomomichi  ,  Oka, Syunsuke  ,  Tokoro, Hiroko

52015-10-06 , Nature Publishing Group , Department of Chemistry, School of Science, The University of Tokyo , CREST, JST , Division of Materials Science, Faculty of Pure and Applied Sciences, University of Tsukuba
ISSN:2045-2322 (online)
UTokyo Research掲載「世界最小ハードフェライト磁石の開発に成功」 URI: http://www.u-tokyo.ac.jp/ja/utokyo-research/research-news/the-worlds-smallest-hard-ferrite-magnet.html
UTokyo Research "The world's smallest hard ferrite magnet" URI: http://www.u-tokyo.ac.jp/en/utokyo-research/research-news/the-worlds-smallest-hard-ferrite-magnet.html
Development of nanometer-sized magnetic particles exhibiting a large coercive field (Hc) is in high demand for densification of magnetic recording. Herein, we report a single-nanosize (i.e., less than ten nanometers across) hard magnetic ferrite. This magnetic ferrite is composed of ε-Fe2O3, with a sufficiently high Hc value for magnetic recording systems and a remarkably high magnetic anisotropy constant of 7.7 × 106 erg cm−3. For example, 8.2-nm nanoparticles have an Hc value of 5.2 kOe at room temperature. A colloidal solution of these nanoparticles possesses a light orange color due to a wide band gap of 2.9 eV (430 nm), indicating a possibility of transparent magnetic pigments. Additionally, we have observed magnetization-induced second harmonic generation (MSHG). The nonlinear optical-magnetoelectric effect of the present polar magnetic nanocrystal was quite strong. These findings have been demonstrated in a simple iron oxide, which is highly significant from the viewpoints of economic cost and mass production.


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