Tatsuo C. Kobayashi
Okayama University
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Featured researches published by Tatsuo C. Kobayashi.
Nature | 2005
Ryotaro Matsuda; Ryo Kitaura; Susumu Kitagawa; Yoshiki Kubota; Rodion V. Belosludov; Tatsuo C. Kobayashi; Hirotoshi Sakamoto; Takashi Chiba; Masaki Takata; Yoshiyuki Kawazoe; Y. Mita
Metal–organic microporous materials (MOMs) have attracted wide scientific attention owing to their unusual structure and properties, as well as commercial interest due to their potential applications in storage, separation and heterogeneous catalysis. One of the advantages of MOMs compared to other microporous materials, such as activated carbons, is their ability to exhibit a variety of pore surface properties such as hydrophilicity and chirality, as a result of the controlled incorporation of organic functional groups into the pore walls. This capability means that the pore surfaces of MOMs could be designed to adsorb specific molecules; but few design strategies for the adsorption of small molecules have been established so far. Here we report high levels of selective sorption of acetylene molecules as compared to a very similar molecule, carbon dioxide, onto the functionalized surface of a MOM. The acetylene molecules are held at a periodic distance from one another by hydrogen bonding between two non-coordinated oxygen atoms in the nanoscale pore wall of the MOM and the two hydrogen atoms of the acetylene molecule. This permits the stable storage of acetylene at a density 200 times the safe compression limit of free acetylene at room temperature.
Journal of the Physical Society of Japan | 2002
H. Shishido; Rikio Settai; Dai Aoki; Shugo Ikeda; Hirokazu Nakawaki; Noriko Nakamura; Tomoya Iizuka; Yoshihiko Inada; Kiyohiro Sugiyama; Tetsuya Takeuchi; K. Kindo; Tatsuo C. Kobayashi; Yoshinori Haga; Hisatomo Harima; Yuji Aoki; Takahiro Namiki; Hideyuki Sato; Yoshichika Onuki
We have studied Fermi surface properties of LaRhIn 5 and CeTIn 5 (T: Co, Rh and Ir) via the de Haas–van Alphen (dHvA) experiment. The Fermi surface of a non-4 f reference compound LaRhIn 5 is quasi...
Journal of the Physical Society of Japan | 2004
Yoshichika Onuki; Rikio Settai; Kiyohiro Sugiyama; Tetsuya Takeuchi; Tatsuo C. Kobayashi; Yoshinori Haga; Etsuji Yamamoto
We present recent advances in the magnetism and superconductivity of rare earth and uranium compounds. Heavy fermions are formed on the basis of the competition between the RKKY interaction and the Kondo effect in these compounds. The application of pressure to these compounds is useful to control the electronic states in the antiferromagnets CeRh 2 Si 2 and CeRhIn 5 , and the ferromagnet UGe 2 . The quadrupole interaction or the quadrupole Kondo effect is found to be responsible for heavy fermions in PrFe 4 P 12 . A rich variety of superconducting properties are demonstrated: superconductivity of CeCoIn 5 and CeRhIn 5 in the vicinity of a quantum critical point, coexistence of ferromagnetism and superconductivity in UGe 2 , and superconductivity based on the quadrupole fluctuations in PrOs 4 Sb 12 , together with the relation between the superconducting transition temperature and the quasi-two dimensionality of the electronic states.
Journal of the Physical Society of Japan | 2004
Teruhiko Akazawa; Hiroyuki Hidaka; Hisashi Kotegawa; Tatsuo C. Kobayashi; Tabito Fujiwara; Etsuji Yamamoto; Yoshinori Haga; Rikio Settai; Yoshichika Onuki
Pressure-induced superconductivity is found in UIr without inversion symmetry. The pressure–temperature phase diagram has been investigated by means of the electrical resistivity and magnetization ...
Journal of the Physical Society of Japan | 2001
Takaki Muramatsu; Naoyuki Tateiwa; Tatsuo C. Kobayashi; Katsuya Shimizu; Kiichi Amaya; Dai Aoki; H. Shishido; Yoshinori Haga; Yoshichika Onuki
The pressure dependence of transport properties in CeRhIn5 was studied up to 8.5 GPa by using a diamond-anvil cell. The electrical resistivity does not follow the T 2 -dependecne of a Fermi liquid nature under any pressure. In this non-Fermi liquid state, superconductivity was observed in a wide pressure range of 1:5 GPa <P <7:6 GPa. The superconducting temperature TC has a double-maximum structure with a minimum at 5.2 GPa. A maximum of TC ¼ 2:2 K was observed at P ¼ 2:5 GPa, where the corresponding electrical resistivity just above TC has the maximum. The upper critical ;eld HC2 and the magnetoresistances were also investigated under pressure.
Review of Scientific Instruments | 2007
Tatsuo C. Kobayashi; Hiroyuki Hidaka; Hisashi Kotegawa; Kenji Fujiwara; M. I. Eremets
An indenter-type high-pressure cell has been developed for electric and magnetic measurements in low-temperature and high-magnetic-field environments. The maximum pressure achieved at low temperatures is more than 4.5 GPa, which is higher than that of a conventional piston-cylinder cell. The typical sample space at maximum pressure is 1.6 mm in diameter and approximately 0.7 mm in depth, and magnetic measurements such as ac-susceptibility and nuclear magnetic resonance can be performed using a miniature coil. All the components of the indenter cell are made of nonmagnetic materials that have enough thermal conductivity for low-temperature experiments using a 3He/4He dilution refrigerator. Another indenter-type cell designed for a commercial superconducting quantum interference device magnetometer is also reported.
Journal of the Physical Society of Japan | 1998
Y. Kitaoka; Tatsuo C. Kobayashi; Akihiro Koda; Hayato Wakabayashi; Yoshihiro Niino; Hirokazu Yamakage; Shinichiro Taguchi; Kiichi Amaya; Kazunari Yamaura; Mikio Takano; Atushi Hirano; Ryoji Kanno
From the 7 Li nuclear magnetic resonance (NMR) and specific heat measurements of LiNiO 2 , consisting of a spin-1/2 triangular lattice, it is demonstrated that the previously suggested spin-glass-like freezing below T s g =8 K, which is caused by defects of Li ions, is not the true ground state, but rather a quantum disordered state is realized without a spin gap. This state is characterized by power-law behavior of the temperature dependence of the specific heat below 0.5 K. A spin-liquid state with short-range ferromagnetic correlations is suggested from new insight into the frustration of orbital ordering for doubly degenerate e g shells in the triangular lattice.
Journal of the Physical Society of Japan | 2001
Naoyuki Tateiwa; Katsumi Hanazono; Tatsuo C. Kobayashi; Kiichi Amaya; Tetsutaro Inoue; Koichi Kindo; Yoshihiro Koike; N. Metoki; Yoshinori Haga; Rikio Settai; Y. Ōnuki
We performed DC-magnetization and neutron scattering experiments under pressure P for a pressure-induced superconductor UGe 2 . We found that the magnetic moment is enhanced at a characteristic temperature T * in the ferromagnetic state, where T * is smaller than a Curie temperature T C . This enhancement becomes remarkable in the vicinity of P C * =1.20 GPa, where T * becomes 0 K and the superconducting transition temperature T SC shows a maximum. The characteristic temperature T * , which decreases with increasing pressure, also depends on the magnetic field.
Journal of the Physical Society of Japan | 2005
Rikio Settai; Tetsuo Kubo; Tomoyuki Shiromoto; Daisuke Honda; H. Shishido; Kiyohiro Sugiyama; Yoshinori Haga; Tatsuma D. Matsuda; Kiyoshi Betsuyaku; Hisatomo Harima; Tatsuo C. Kobayashi; Y. Onuki
We have studied a change of the Fermi surface in an antiferromagnet CeIn 3 via the de Haas–van Alphen experiment under pressure up to 3 GPa. With increasing pressure P , the Neel temperature T N =10 K decreases and becomes zero at a critical pressure P c ≃2.6 GPa. In the pressure region P > P c , we have observed a large main Fermi surface named a , which indicates that the electronic state of 4 f electron in CeIn 3 changes from localized to itinerant at P c , as observed in the similar antiferromagnets CeRh 2 Si 2 and CeRhIn 5 . The cyclotron effective mass m c * of this main Fermi surface is extremely enhanced around P c : m c * ≃60 m 0 at 2.7 GPa for the magnetic field along the direction.
Molecular Crystals and Liquid Crystals | 1997
Wasuke Mori; Tatsuo C. Kobayashi; Junji Kurobe; Kuichi Amaya; Yasuo Narumi; T. Kumada; Koichi Kindo; Hiroko Aruga Katori; T. Goto; N. Miura; Satoshi Takamizawa; Hirokazu Nakayama; Kizashi Yamaguchi
Abstract Magnetic properties of oxygen physisorbed in Cu-trans-1,4-cyclohexanedicarboxylic acid having one-dimensional micropores are studied. O2 is well known as a magnetic molecule with S=1. In the case of the low adsorption, temperature dependence of the susceptibility shows the Schottky-type broad peak and the high-field magnetization process has a step at around 34T with saturation moment of 2 μ B/O2. These results are interpreted by the dimer model of S=½ with an antiferromagnetic exchange interaction. Broadening of the step of magnetization with increasing the adsorption may be due to the inter-dimer interaction or the distribution of the intra-dimer exchange interaction. Linear magnetization process which is characteristic of one-dimensional Heisenberg antiferromagnet has not been observed even in the full pore region.