Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
Volume 86 , Issue 8
Showing 1-15 articles out of 15 articles from the selected issue
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  • Shin-ichi Ohkoshi, Hiroko Tokoro
    2013 Volume 86 Issue 8 Pages 897-907
    Published: August 15, 2013
    Released: August 15, 2013
    [Advance publication] Released: June 22, 2013
    JOURNALS FREE ACCESS
    Iron oxide Fe2O3 has four polymorphs: α-, β-, γ-, and ε-phases. α-Fe2O3 (hematite) and γ-Fe2O3 (maghemite) are abundant in nature, whereas β- and ε-Fe2O3 phases are very rare and must be artificially synthesized in the laboratory. Pure ε-Fe2O3 phase was first synthesized in 2004 using a combination of reverse-micelle and sol–gel techniques, and it shows the largest coercive field value (Hc) among metal oxide-based magnets of 20 kOe at room temperature. Successively, several kinds of metal-substituted ε-iron oxides, ε-MxFe2−xO3 (M = In, Ga, and Al), have been synthesized, and their magnetic properties are controlled by the degree of the metal substitution. Such iron oxides with a high Hc are attractive from industrial application viewpoints, e.g., magnetic recordings and electromagnetic wave absorbers. A series of ε-MxFe2−xO3 shows high-frequency electromagnetic wave absorption due to zero-field ferromagnetic resonance at 35–182 GHz in the millimeter range, which is useful for next-generation high-speed wireless communications. In this article, we describe (i) the synthesis, crystal structure, and magnetic properties of ε-Fe2O3, (ii) generation mechanism of ε-Fe2O3, the origin of the gigantic coercive field, and theoretical analysis of magnetic ordering, (iii) metal-substituted ε-iron oxides, ε-MxFe2−xO3, and (iv) electromagnetic wave absorption in the millimeter wave range.
    ε-Iron oxide (ε-Fe2O3) and metal-substituted ε-iron oxides (ε-MxFe2−xO3), which exist as nanoscale size particles, demonstrate gigantic magnetic coercive fields of up to 20 kOe and high-frequency electromagnetic wave absorption. Fullsize Image
     
BCSJ Award Article
  • Raeeun Lee, Asako Igashira-Kamiyama, Mitsutaka Okumura, Takumi Konno
    2013 Volume 86 Issue 8 Pages 908-920
    Published: August 15, 2013
    Released: August 15, 2013
    JOURNALS FREE ACCESS
    An optically active AuI4CoIII2 complex with mixed D-penicillaminate (D-pen) and 1,2-bis(diphenylphosphino)ethane (dppe), [Au4Co2(dppe)2(D-pen)4]2+, was selectively formed from [Au2(dppe)(D-pen)2]2− and CoIII. When this complex was crystallized with monovalent anions (ClO4, BF4, NO3, Cl, Br, and N3), the AuI4CoIII2 complex cations were self-assembled to form +12-charged supramolecular octahedrons that are closely packed in a face-centered cubic (fcc) structure. In this structure, ten monovalent anions are accommodated in each hydrophilic tetrahedral interstice to create an adamantane-shaped anionic cluster, while two anions are each encapsulated in each octahedral interstice and in the center of each supramolecular octahedron. The use of divalent anions (SO42− and SiF62−) also produced an analogous fcc structure made up of the +12-charged supramolecular octahedrons. In this case, six divalent anions are accommodated in each hydrophilic tetrahedral interstice to form an octahedron-shaped anionic cluster, completing a giant zinc blende lattice structure where all cations and anions are separately aggregated into the +12-charged octahedrons and the −12-charged octahedrons, respectively. The site selective aggregation of two kinds of inorganic anions (PF6/Br, BF4/Br, and NO3/Br) in the fcc structure, along with the synthesis and characterization of an analogous AuI4CrIII2 complex, is also reported.
    The cationic AuI4MIII2 (M = Co and Cr) hexanuclear complexes are crystallized with certain inorganic anions to form ionic crystals, in which inorganic anions are aggregated into amazing anionic clusters accompanied by the aggregation of the AuI4MIII2 cations into supramolecular octahedrons. Fullsize Image
     
 
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