Browsing by Author "Tanaka, Katsuhisa"

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    Giant faraday rotation through ultra-small Fe0n clusters in superparamagnetic FeO-SiO2 vitreous films
    (Hoboken : Wiley, 2017) Nakatsuka, Yuko; Pollok, Kilian; Wieduwilt, Torsten; Langenhorst, Falko; Schmidt, Markus A.; Fujita, Koji; Murai, Shunsuke; Tanaka, Katsuhisa; Wondraczek, Lothar
    Magnetooptical (MO) glasses and, in particular, Faraday rotators are becoming key components in lasers and optical information processing, light switching, coding, filtering, and sensing. The common design of such Faraday rotator materials follows a simple path: high Faraday rotation is achieved by maximizing the concentration of paramagnetic ion species in a given matrix material. However, this approach has reached its limits in terms of MO performance; hence, glass‐based materials can presently not be used efficiently in thin film MO applications. Here, a novel strategy which overcomes this limitation is demonstrated. Using vitreous films of xFeO·(100 − x)SiO2, unusually large Faraday rotation has been obtained, beating the performance of any other glassy material by up to two orders of magnitude. It is shown that this is due to the incorporation of small, ferromagnetic clusters of atomic iron which are generated in line during laser deposition and rapid condensation of the thin film, generating superparamagnetism. The size of these clusters underbids the present record of metallic Fe incorporation and experimental verification in glass matrices.
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    Microstructure and magnetic character of terbium borate glass
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1992) Tanaka, Katsuhisa; Ohyagi, Tomohito; Hirao, Kazuyuki; Soga, Naohiro; Mori, Hirotaro
    Microstructure and magnetic character of 30 Tb2O3 · 70 B2O3 glass have been examined by means of high-resolution transmission electron microscopy and magnetization measurements. Although no trace of crystahine phases was observed in the electron diffraction pattern, the transmission electron micrograph revealed that there exist clusters, the size of which is about 1 nm, in the present glass. The magnetization measurements showed that this glass is paramagnetic at room temperature. However, the magnetization is high enough for the glass to adhere to a permanent magnet in the Nd-Fe-B system at room temperature.