H Kobayashi

Nihon University, Edo, Tōkyō, Japan

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Publications (518)1189.33 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The magnetoresistance of λ-(BETS)2FeCl4 was measured along the needle axis of the crystal to determine the pressure and magnetic field dependences of the coupled metal-insulator and antiferromagnetic transition temperature (TMI, TN). TMI decreases when applying pressure and/or magnetic field. The TMI vs H curve shows an inflection point (H1). The anomaly observed around 1 T (H1) corresponds to the spin-flop transition observed by the SQUID measurements. The magnetization (M) of the oriented polycrystalline sample of λ-(BETS)2FeCl4 was measured at 2–15 K in a magnetic field of 0.01–7 T. The magnitude of the characteristic drop of M observed for the field parallel to the c axis (ΔM∥) becomes small above 1.2 T but remains almost constant above 4.5 T.
    Solid State Communications 01/2013; · 1.53 Impact Factor
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    ABSTRACT: Magnetic torque measurements have been carried out for two-dimensional magnetic-field-induced organic superconductor λ-(BETS)2FeCl4, where BETS stands for bis(ethylenedithio)tetraselenafulvalene, to investigate the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase. The in-plane upper critical field of the field-induced-superconducting phase steeply decreases with decreasing temperature below 2.2 K. The in-plane field dependence of the diamagnetic susceptibility shows a significant decrease below 25 T at low temperatures, showing that magnetic fluxes are less excluded from the sample. These results show the presence of the FFLO phase with the tricritical point between the FFLO, homogeneous superconducting, and paramagnetic metallic phases at 2.2 K and 23 T. The stability of the FFLO phase is also investigated as a function of the magnetic field angle and compared with theories.
    Physical review. B, Condensed matter 05/2012; 85(17). · 3.77 Impact Factor
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    ABSTRACT: We have studied periodic orbit resonances (PORs) in order to probe the topology of the Fermi surface (FS) of the quasi-1D organic conductor (TMTSF)2ClO4 and the quasi-2D organic conductors κ-(ET)2Cu(NCS)2 and κ-(ET)2I3. The FS of (TMTSF)2ClO4 consists of a pair of weakly corrugated open sheets, while κ-(ET)2Cu(NCS)2 and κ-(ET)2I3 additionally possess warped cylindrical FS sections. In this paper, we review the POR technique for the straightforward case of (TMTSF)2ClO4. We then report on a detailed study of the FS topology for κ-(ET)2Cu(NCS)2.
    International Journal of Modern Physics B 01/2012; 18(27n29). · 0.46 Impact Factor
  • H. B. Cui, D. Graf, J. S. Brooks, H. Kobayashi
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    ABSTRACT: A Reply to the Comment by Dafang Li, Yanming Ma, and Jun Yan.
    Physical Review Letters 04/2010; 104(13). · 7.73 Impact Factor
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    ABSTRACT: The four-probe resistivity measurements were performed on the molecular crystals of TMTTeN (=tetramethyltetratelluronaphthalene) and [Ni(ptdt)2] (ptdt=propylenedithio tetrathiafulvalenedithiolate) by using a diamond anvil cell (DAC) up to 30 and 21GPa, respectively. In spite of extremely large enhancement of room-temperature conductivity (∼350Scm−1 at 25.4GPa) and metallic behavior at low temperatures (25–65K at 25.4GPa), the pressure-induced metallic state could not be observed in TMTTeN up to 30GPa at least around room temperature. The resistivity of [Ni(ptdt)2] decreased with increasing pressure and became approximately 10−2Ωcm at 18Gpa. The temperature dependence of the resistivity exhibited a weakly semiconducting behavior. At around 19.5GPa, [Ni(ptdt)2] showed weakly metallic behavior down to low temperature. However, this pressure-induced metallic state was not stable. At 20.7GPa, the resistivity increased again below 40K.The four-probe resistance measurements were also performed on the extremely brittle thin-plate microcrystals of single-component antiferromagnetic molecular conductor [Au(tmdt)2]. The resistance (R) decreased continuously with decreasing temperature (T). Except for a slight bending of the R−T curve at around the magnetic transition temperature (TN=110K), no resistance anomaly was observed. Nonetheless, the existence of the metallic state below TN was confirmed for the first time from the results of single-crystal resistance measurement.The precise crystal structure examinations were performed on [Au(tmdt)2] by the powder X-ray diffraction data at the temperature range of 9–300K.
    Physica B Condensed Matter 01/2010; 405(11). · 1.33 Impact Factor
  • H. TANAKA, A. KOBAYASHI, H. KOBAYASHI
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    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    ChemInform 01/2010; 29(18).
  • [Show abstract] [Hide abstract]
    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    ChemInform 01/2010; 27(27).
  • [Show abstract] [Hide abstract]
    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    ChemInform 01/2010; 28(44).
  • [Show abstract] [Hide abstract]
    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    ChemInform 01/2010; 28(43).
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    ABSTRACT: Shubnikov–de Haas and angular dependent magnetoresistance oscillations have been used to explore the role of anion size, magnetic moment, and disorder in the organic conductors κ‐(BETS)2GaBr4κ‐(BETS)2GaBr4 and κ‐(BETS)2FeCl2Br2κ‐(BETS)2FeCl2Br2 in the isomorphic class κ‐(BETS)2Ga1‐xFexCl4‐yBryκ‐(BETS)2Ga1‐xFexCl4‐yBry. The results, combined with previous work, show correlations between the anion composition (Ga1‐xFexCl4‐yBry)(Ga1‐xFexCl4‐yBry) and the superconducting transition temperature, effective mass, Fermi surface topology, and the mean free path.
    Physica B Condensed Matter 01/2010; 405(11):S295–S298. · 1.33 Impact Factor
  • Source
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    ABSTRACT: Shubnikov-de Haas and angular dependent magnetoresistance oscillations have been used to explore the role of anion size, magnetic moment, and disorder in the organic conductors kappa-(BETS)_2GaBr_{4} and kappa-(BETS)_2FeCl_{2}_Br_{2} in the isomorphic class kappa-(BETS)_2Ga_{1-x}Fe_{x}Cl_{4-y}_Br_{y}. The results, combined with previous work, show correlations between the anion composition (Ga_{1-x}Fe_{x}Cl_{4-y}_Br_{y}) and the superconducting transition temperature, effective mass, Fermi surface topology, and the mean free path. Comment: 5 pages, 6 figures
    09/2009;
  • H B Cui, D Graf, J S Brooks, H Kobayashi
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    ABSTRACT: Germanium (Ge) becomes an "artificial metal" and a superconductor (T(c) approximately 5 K) above the pressure-induced semiconductor-(diamond structure)-to-metal (beta-Sn structure) transition at 10 GPa. We report single crystal resistance studies of the pressure-dependent metallic and metastable phases in the range 2.6 to 23 GPa, and show for a controlled pressure release, Ge is a metastable metal below 3 GPa. We find Ge has a superconducting upper critical field of 300 Oe (at 10.7 GPa and 1.8 K), above which a positive magnetoresistance consistent with that of a compensated closed orbit metal is observed.
    Physical Review Letters 07/2009; 102(23):237001. · 7.73 Impact Factor
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    ABSTRACT: New bis(ethylenedithio)tetraselenafulvalene (BETS) based radical cation salts with tetrahedral dianions [CdBr4]2− and [HgBr4]2− of the (BETS)4MBr4(PhBr) composition were prepared by electrochemical crystallization. Room-temperature crystal structure of (BETS)4CdBr4(PhBr) determined by single crystal X-ray diffraction involves BETS radical cation layers of the θ-type packing and insulating layers consisting of [CdBr4]2− anions and PhBr molecules. In the neighboring conducting layers, the stacks are arranged perpendicular to each other. A metal-to-metal transition within 225–230K range was found in both (BETS)4CdBr4(PhBr) and (BETS)4HgBr4(PhBr). The behavior of electrical resistivity of these salts differs substantially along and across conducting layers. The study of magnetoresistance of (BETS)4HgBr4(PhBr) revealed weak Shubnikov-de Haas oscillations in fields higher than 6T.
    Synthetic Metals 01/2009; 159(11):1072-1076. · 2.11 Impact Factor
  • H. Kobayashi, K. Ohmi, K. Ichino, T. Kunimoto
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    ABSTRACT: In this paper, we discuss the present status of electroluminescence (EL) of inorganic materials. From 1970's, the main research was made on multicolor and fullcolor EL. Finally blue inorganic EL of BaAl2S4:Eu was developed, resulting in fullcolor EL-TV using “color by blue®” by iFire Technology. Very recently, a new ultra bright inorganic EL of dc driven at lower than 10 V has been developed. These three findings will stimulate the researches on inorganic EL, which slowed down and were not active in the past two decades. Some new findings are expected. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
    Physica Status Solidi (A) Applications and Materials 01/2008; 205(1):11 - 14. · 1.46 Impact Factor
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    ABSTRACT: Magnetotransport properties of two isostructural salts, the superconducting λ-(BETS)2GaCl4 phase and the first organic conductor containing magnetic Fe3+ ions, λ-(BETS)2FeCl4, where BETS is bis(ethylenedithio)tetraselenafulvalene, have been studied up to 37 T. The previously reported sharp metal-insulator phase transition occurring at 8 K under ambient pressure for λ-(BETS)2FeCl4 is suppressed when applying magnetic fields > 10 T. This unusual phenomenon may be connected to a field-induced ferromagnetic ordering of the Fe3+-ions moments. This could result in some kind of "decondensation" of the carriers, initially condensed below 8 K, into a field-restored highly conducting state (FRHCS). The temperature-magnetic-field (T-H) phase diagram is presented. The angle dependence of the critical field Hc2 has been determined for the superconducting λ-(BETS)2GaCl4 phase at 4.2 K.
    EPL (Europhysics Letters) 07/2007; 28(6):427. · 2.26 Impact Factor
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    ABSTRACT: Human Vgamma2Vdelta2 T cells recognize nonpeptide antigens, such as isoprenoid pyrophosphomonoester intermediates, alkylamine compounds, and bisphosphonate drugs, as well as some tumor cells. Although attempts have been made to derive novel cancer immunotherapies based on the discovery of these unconventional antigens, effective therapies remain to be developed. Here, we synthesized a series of pyrophosphate-containing compounds and examined the chemical requirements for the recognition of pyrophosphomonoester antigens by gammadelta T cells. The structural analysis clearly demonstrated that a proximal methylene moiety plays a crucial role in the stimulatory activity of the antigens. For optimal gammadelta T cell proliferation, we find that the use of human serum albumin was preferred and that pyrophosphomonoesters were superior to nitrogen-containing bisphosphonate compounds. Using these techniques, we have successfully expanded gammadelta T cells from healthy donors as well as from cancer patients using one of the most active compounds, 2-methyl-3-butenyl-1-pyrophosphate (2M3B1PP). The resulting expanded gammadelta T cells exhibited potent, cytotoxic activity against a wide variety of tumor cell lines. Even gammadelta T cells from a patient with advanced liver carcinoma efficiently responded to 2M3B1PP and exhibited strong cytotoxic activity against tumor cells. The pretreatment of tumor cells with nonpeptide antigens was essential for efficient cytotoxicity via TCR-gammadelta. The present study suggests a novel strategy for cancer immunotherapy using synthetic small pyrophosphate-containing compounds and nitrogen-containing bisphosphonates.
    Medicinal Chemistry 02/2007; 3(1):85-99. · 1.37 Impact Factor
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    ABSTRACT: Chiral magnets are obtained by inclusion of chiral guest molecules into the channels of an achiral nanoporous ferrimagnet consisting of the Mn3(HCOO)6 (1) framework. Insertion of the R or the S enantiomer of 2-chloropropan-1-ol (CH3C*HClCH2OH) in the chiral pores of the previously emptied framework (space group P21/c) results in the two corresponding chiral solids (1R and 1S, space group P21), while insertion of a racemic mixture of the two enantiomers retains the achirality of the host for the meso solid (1RS, space group P21/c). The R guest is ordered in the M channels while the S guest is ordered in the P channels. In contrast, the R guests in the P channels and the S guests in the M channels are disordered on two crystallographic orientations. For the racemic mixture of the two enantiomers in 1RS, random disorder of guests in both channels is observed. Thus, the localization of the guest molecule depends on the nature of the surface to recognize the guest of a particular chirality. The guest inclusion compounds are thermally stable. The 1R and 1S compounds are optically active. All the compounds adopt a ferrimagnetic ground state. Compared to the host framework of 1 without guest, the Curie temperature decreases for both 1R and 1S but increases for 1RS. The additional interactions between the framework and the inserted guest alcohols strengthen the lattice via hydrogen bonds and other electrostatic forces, and it might account for the significant lowering of the lattice contribution as well as the magnetic component to the specific heat capacity upon guest loading.
    Advanced Functional Materials 01/2007; 17(4):577 - 584. · 9.77 Impact Factor
  • Low Temperature Physics - LOW TEMP PHYS. 01/2007; 142:609-612.
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    ABSTRACT: Se77-NMR spectrum and frequency shift measurements in the paramagnetic metal and antiferromagnetic insulating phases are reported for a small single crystal of the organic conductor lambda-(BETS)2FeCl4 as a function of temperature (T) and field alignment for an applied magnetic field B0=9T . The results show that in the low T limit, where the localized Fe3+ spins (Sd=5/2) are almost fully polarized, the conduction electrons (Se pi electrons, spin spi=1/2 ) in the BETS molecules experience an exchange field (Bpid) from the Fe3+ spins with a value of -32.7±1.5T at 5K and 9T aligned opposite to B0 . This large negative value of Bpid is consistent with that predicted by the resistivity measurements and supports the Jaccarino-Peter internal field-compensation mechanism being responsible for the origin of field-induced superconductivity.
    Physical review. B, Condensed matter 01/2007; 76. · 3.77 Impact Factor
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    ABSTRACT: Magneto-optical measurements have been performed in organic conductors β''-(BEDT-TTF)2CsCd(SCN)4 and λ-(BETS)2FeCl4. Although the zero magnetic field ground state of β''-(BEDT-TTF)2CsCd(SCN)4is considered as the density wave state, periodic orbit resonances (POR's) attributed to quasi-one-dimensional (Q1D) and quasi-two-dimensional (Q2D) Fermi surfaces (FS's) have been observed above 6 T. The existence of these FS's are predicted by the band calculation based on room temperature lattice parameters. This result may suggest the destruction of the density wave state at 6 T, and the primal metallic state revives in the high field phase above 6 T. In the case of λ-(BETS)2FeCl4, large changes of the transmission intensity of electromagnetic waves around 10 T, which correspond to the insulator-metal transition, have been observed. However, no POR-like resonance has been observed. This may be due to the restriction of the observed frequency-field region.
    Journal of Physics Conference Series 12/2006; 51(1):359.

Publication Stats

5k Citations
1,189.33 Total Impact Points

Institutions

  • 2009–2012
    • Nihon University
      • Department of Chemistry
      Edo, Tōkyō, Japan
    • Florida State University
      • Department of Physics
      Tallahassee, FL, United States
  • 1998–2010
    • Tottori University
      • Department of Electrical and Electronic Engineering
      TTJ, Tottori, Japan
  • 1987–2010
    • The University of Tokyo
      • • Department of Chemistry
      • • Department of Applied Physics
      • • Institute for Solid State Physics
      Edo, Tōkyō, Japan
    • Higashi Nippon International University
      Higashimurayama-shi, Tōkyō, Japan
  • 1984–2010
    • Toho University
      • • Department of Chemistry
      • • Faculty of Science
      Edo, Tōkyō, Japan
  • 1999–2007
    • Institute for Molecular Science
      Okazaki, Aichi, Japan
    • Health Sciences University of Hokkaido
      • Department of Oral and Maxillofacial Surgery
      Tōbetsu, Hokkaido, Japan
    • Gakushuin University
      • Department of Physics
      Tokyo, Tokyo-to, Japan
  • 2006
    • National Institute for Materials Science
      Tsukuba, Ibaraki, Japan
    • Tokushima Bunri University
      Shido, Kagawa, Japan
  • 2004
    • Miyazaki University
      Миядзаки, Miyazaki, Japan
  • 2002–2004
    • Gunma University
      • Institute for Molecular and Cellular Regulation
      Maebashi, Gunma Prefecture, Japan
    • Saitama University
      • Faculty of Science
      Saitama, Saitama, Japan
    • Tohoku University
      • Department of Physics
      Sendai, Kagoshima, Japan
    • Nagasaki University
      • Department of Pharmacology
      Nagasaki-shi, Nagasaki-ken, Japan
  • 1992–2004
    • Osaka University
      • • Institute of Scientific and Industrial Research
      • • Department of Integrated Medicine
      • • Division of Applied Chemistry
      Suika, Ōsaka, Japan
  • 2003
    • University of Florida
      • Department of Physics
      Gainesville, FL, United States
  • 1990–2003
    • Saitama Cancer Center
      • Saitama Cancer Center Hospital
      Saitama, Saitama, Japan
  • 1983–2002
    • University of Occupational and Environmental Health
      • • Department of Physiology
      • • School of Medicine
      Kitakyūshū, Fukuoka, Japan
  • 2001
    • Yokohama National University
      Yokohama, Kanagawa, Japan
    • Tsukuba Research Institute
      Edo, Tōkyō, Japan
    • Nikko Memorial Hospital
      Hidachi, Ibaraki, Japan
    • Center for Infertility and Human Reproduction
      Barcino, Catalonia, Spain
  • 2000–2001
    • Kyoto University
      • Graduate School of Medicine / Faculty of Medicine
      Kyoto, Kyoto-fu, Japan
    • University of Malaya
      • Department of Physics
      Kuala Lumpur, Kuala Lumpur, Malaysia
  • 1999–2001
    • Tokyo Women's Medical University
      • Department of Urology
      Edo, Tōkyō, Japan
  • 1967–2001
    • Hokkaido University Hospital
      • Division of Dermatology
      Sapporo, Hokkaidō, Japan
  • 1982–1999
    • Hokkaido University
      • • Department of Dermatology
      • • Division of Chemistry
      Sapporo-shi, Hokkaido, Japan
  • 1997
    • Tokyo Medical and Dental University
      • Department of Internal Medicine
      Edo, Tōkyō, Japan
  • 1996
    • Kyoto Daini Red Cross Hospital
      Kioto, Kyōto, Japan
  • 1995
    • University of Tsukuba
      • Applied Physics
      Tsukuba, Ibaraki, Japan
  • 1994
    • Nagoya Second Red Cross Hospital
      Nagoya, Aichi, Japan
  • 1993
    • Tokyo University of Science
      Edo, Tōkyō, Japan
  • 1991
    • Paul Sabatier University - Toulouse III
      Tolosa de Llenguadoc, Midi-Pyrénées, France
  • 1988–1991
    • Keio University
      • School of Medicine
      Tokyo, Tokyo-to, Japan
  • 1980–1988
    • University of Milan
      • Department of Pharmacological Sciences
      Milano, Lombardy, Italy
  • 1986
    • Harbin Medical University
      Charbin, Heilongjiang Sheng, China