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Werheit H.,University of Duisburg - Essen | Filipov V.,Frantsevich Institute for Problems of Materials Science | Kuhlmann U.,University of Duisburg - Essen | Kuhlmann U.,Pirelli SpA | And 8 more authors.
Science and Technology of Advanced Materials | Year: 2010

We present Raman spectra of numerous icosahedral boron-rich solids having the structure of α-rhombohedral, β-rhombohedral, α-tetragonal, β-tetragonal, YB66, orthorhombic or amorphous boron. The spectra were newly measured and, in some cases, compared with reported data and discussed. We emphasize the importance of a high signal-to-noise ratio in the Raman spectra for detecting weak effects evoked by the modification of compounds, accommodation of interstitial atoms and other structural defects. Vibrations of the icosahedra, occurring in all the spectra, are interpreted using the description of modes in α-rhombohedral boron by Beckel et al. The Raman spectrum of boron carbide is largely clarified. Relative intra- and inter-icosahedral bonding forces are estimated for the different structural groups and for vanadium-doped β-rhombohedral boron. The validity of Badger's rule is demonstrated for the force constants of inter-icosahedral B-B bonds, whereas the agreement is less satisfactory for the intra-icosahedral B-B bonds. © 2010 National Institute for Materials Science.

Shiroyama T.,National Institute for MaterialsScience | Abe T.,National Institute for MaterialsScience | Takahashi Y.,National Institute for MaterialsScience | Hono K.,National Institute for MaterialsScience
IEEE Transactions on Magnetics | Year: 2013

We have studied the microstructures and magnetic properties of FePt-segregant granular films to achieve an ideal media structure on glass substrates for thermally assisted magnetic recording. Although FePt-C granular films show an excellent in-plane structure, it does not have a good surface roughness. Meanwhile, FePt-SiO2 granular films have a smooth surface and an interconnected in-plane microstructure. Therefore, to obtain both a surface with a small roughness and well-isolated small columnar grains, we have selected four metal oxides, MOx (M=Nb, W, Zr and Al) as segregants, which are expected to have a driving force for the phase separation between FePt-C and FePt-SiO2 based on thermodynamic evaluation. In this paper, we introduce the ground for selecting these materials as segregants and then show the microstructure and magnetic properties of FePt-MOx granular films. © 2013 IEEE.

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