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Research Results
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1998
2005
Nov. 2005
  There are no reports of quantum oscillation phenomena (dHvA effect) in plutonium compounds because of the strong damage due to the high radio activity. We have succeeded in growing a high quality single crystal of PuIn3 and observed the dHvA effect in a short period of time. This is the first observation of the Fermi surfaces in plutonium compounds. The 5f electrons of plutonium atom are itinerant with heavy effective mass. The result was reported in "Nikkan-Kogyo Shimbun" on November 11. The paper was selected for "Papers of Editor's Choice" in J. Phys. Soc. Jpn.. The work has been done in collaboration with Japan Atomic Energy Agency, Kyoto-Sangyo University and Osaka University.
Prof. Shiokawa group (Radiochemistry of Metals),
International Research Center for Nuclear Materials Science
Aug. 2005
   Real space imaging of the metal-insulator phase separation of micrometer scale has been successfully obtained in the highly correlated organic conductors κ-(BEDT-TTF)2Cu[N(CN)2]Br. The phase separation has consisted of the metal and the insulating domains of several 10 micrometer scale. This imaging has become possible by means of the scanning micro-region infrared spectroscopy (SMIS) method using high brilliance and directional infrared light from synchrotron radiation of SPring-8. The phase separation has been observed in the vicinity of the first order Mott transition of the κ-(BEDT-TTF)2Cu[N(CN)2]Br of which band width has been controlled by the partial substitution with the deuterated BEDT-TTF molecule. This work were performed in collaboration with Japan Synchrotron Radiation Institute. And the results were published in J. Phys. Soc. Jpn. 74, 2351 (2005), selected as Papers of Editor’s Choice, and appeared in some newspapers, Nikkan-Kogyo (August 12), Nikkei-Sangyo (August 15), and Kagaku-Shinbun (August 26).
Aug. 2005
  The characteristic electronic excitations of the copper oxide superconductor have been observed by the resonant inelastic x-ray scattering (RIXS) method using synchrotron radiation in SPring-8 facility. This study was cooperative work with JAERI. The results were published in Phys. Rev. Lett. on May 12 and May 26, as well as in Nikkan-Kogyo newspaper on August 11, 2005.One of the papers was selected in "Virtual Journal of Applications of Superconductivity".
Prof. Maekawa group(Theory of Solid State Physics)
July. 2005
  We succeeded in generating of a high magnetic field up to 18.1T by the cryogen-free superconducting magnet by the collaboration with Toshiba Co. Ltd.. Since we have demonstrated the world’s first 4T cryogen-free superconducting magnet in 1992, the 15 T cryogen-free superconducting magnet was successfully developed by our group. This time, we improved greatly the generating magnetic field up to 18.1 T by the newly developed cryogen-free superconducting magnet, which consists of a high-Tc oxide-superconducting insert coil using Bi2223 tapes. Since a high- Tc oxide superconductor was discovered, nineteen years have passed. However, there was not yet practical high field power application using high- Tc superconductors so far. The cryogen-free superconducting magnets have many advantages of cost, safety, convenience, and multipurpose, in comparison with the conventional superconducting magnet operated in liquid helium bath. It is expected that the high magnetic fields up to 20 T will be easily available for wide research area through this accomplishment near future. This work appeared in a newspaper of the Nikkei-Kogyo and will be presented at Japan Cryogenic meeting, which will be held at the Toki-messe, Niigata on November 21, 2005.
July. 2005
  A new nanoporous metal-organic-complex materials which selectively absorb and purify acetylene molecules were firstly created by Prof. Susumu Kitagawa and his group in Kyoto University. The structure of this complex has been determined by using a high-density neutron beam in Spring-8 facility. Kawazoe group has performed a large scale ab initio simulation by using the supercomputer SR-8000 at IMR to analyze the mechanism of the selective absorption of the acetylene molecules in this complex. Acetylene is used heavily in industry as the fuel for high-temperature burning and starting materials for chemical and electrical industries. Since it explode easily under high-pressure, it has been impossible to condense the gas to store and carry it in cheep cost. The present nanoporous materials solved these fundamental problems by completely different method, and it is expected that it will be used in industries. The results of this successful collaboration were published in the journal Nature on 14th July 2005, and reported by NHK, Nikkei-Nanotechnology, and several important newspapers.
Jun. 2005
  We have succeeded in growing single crystals of a plutonium based superconductor PuRhGa5, and clarified the mechanism of superconductivity. The upper critical field Hc2 was found to be very anisotropic. From Ga NQR study, the superconducting gap on the Fermi surface was found to be anisotropic with line node gap. These results indicate that new mechanism of superconductivity due to the magnetic fluctuation is realized on PuRhGa5. The result was reported in "Science News" on June 10, "Nikkan-Kogyo Shimbun" on June 17, and broadcasted by NHK. The paper was selected as "Papers of Editor's Choice". The work has been done in collaboration with Japan Atomic Energy Research Institute and Osaka University.
Prof. Shiokawa group (Radiochemistry of Metals),
International Research Center for Nuclear Materials Science
May. 2005
  Recent discovery of the high-Tc superconductivity in Pu compounds reveals that it is important to clarify the electronic states experimentally in the transuranium compounds. Nevertheless, there are no experimental reports because of the high radioactivity. We succeeded in growing high quality single crystals of NpGe3 and NpRhGa5 and observed the de Haas-van Alphen effect. The Fermi surfaces were determined by the experiments and theoretical calculations consistently. The 5f electron of Np plays a role of both conductivity and magnetism, forming heavy electronic states. The result was published in J. Phys.: Condens. Matter and the article has been selected for "IOP Select". The result was also reported on the top page of Kahoku-Shimpo on May 18. The work has been done in collaboration with Osaka University, Kyoto-Sangyo University and Japan Atomic Research Institute.
Prof. Shiokawa group (Radiochemistry of Metals),
International Research Center for Nuclear Materials Science
Apr. 2005
  We succeeded in generating of a high magnetic field up to 27.5T by unique cryogen-free hybrid magnet by the collaboration with Sumitomo Heavy Industries Co. Ltd.. This is the world record of the magnetic field generation by the cryogen-free hybrid magnet. A hybrid magnet consists of an outer superconducting magnet with a large bore and an inner water-cooled resistive magnet. Ordinary hybrid magnets, which are equipped at several high field laboratories in the world, need a large amount of liquid helium for operation and limit to an experimental time due to refilling liquid helium. A cryogen-free hybrid magnet, however, can provide a long experimental time because of the operation without liquid helium. Since we already developed a 22.7 T cryogen-free hybrid magnet a few years ago as the first step, we improved the highest magnetic field generation by the cryogen-free hybrid magnet this time. The great progress of the materials research and industrial application in high magnetic fields is expected. This work appeared in newspapers such as Nikkan-Kogyo, Kagaku-Kogyo-Nippou and Kahoku-Shimpo and will be presented at Japan Cryogenic meeting, which will be held at the University of Tokyo on March 31, 2005.
Apr. 2005
  The development of metal buffer layers and chemical lift-off process can supply GaN template substrates and new process for high brightness LEDs, and results in low cost process which give strong impacts on optical and electronic devices. Instead of conventional low-temperature buffer layers, We succeed in growing high crystallinity GaN by inserting metal buffer layers in between sapphire substrates and GaN epitaxial layers, which enable to chemically lift-off LED structures from the sapphire substrates by selective etching of metal buffer layers. Such novel device processes will contribute to realizing novel and various lighting devices based on high-brightness LEDs. The result was reported in the newspapers of Nikkan-Kogyo, Kahoku-Shimpo (on Apr. 7) and Ashahi (on Apr. 8), and broadcast by NHK.
Prof. Yao group (Physics of Electronic Materials)