研究実績/Research Results
"Single crystal growth of uranium-based magnetic superconductors"
Nagoya Univ., Prof. N. K. Sato
The first example in which superconductivity is induced by ferromagnetic spin fluctuations in the ferromagnet UCoGe[1-2].
[1] T. Hattori, Y. Ihara, Y. Nakai, K. Ishida, Y. Tada, S. Fujimoto, N. Kawakami, E. Osaki, K. Deguchi, N. K. Sato, and I. Satoh, Phys. Rev. Lett. 108, 066403 (2012)
[2] K. Deguchi, E. Osaki, S. Ban, N. Tamura, Y. Simura, T. Sakakibara, I. Satoh, and N. K. Sato, J. Phys. Soc. Jpn. 79, 083708 (2010).
Schematic illustration of a superconducting phase diagram where a spontaneous vortex state emerges as a result of the compromise of the two competitive orders; a vortex state induced by spontaneous magnetization can exist even at zero external magnetic field in UCoGe (right panel), in contrast to a regular type-II superconductor (left panel).
"Magnetic anisotropy controlling of f-metal complexes"
Nara Woman’s Univ., Prof. T. Kajiwara
Lanthanide and actinide complexes were widely investigated as candidates for quantum nano magnets, such as a single-molecule magnet (SMM) or a single-chain magnet (SCM), in which each molecule shows superparamagnetic behavior below Tc. We have synthesized the first example of a structurally designed Er(III) SMM[3].
[3] A. Yamashita, A. Watanabe, S. Akine, T. Nabeshima, M. Nakano, T. Yamamura, T. Kajiwara, Angew. Chem. Int. Ed., 50, 4016 (2011).
Molecular structure of Er(III)Zn(II)3 wheel-shaped tetranuclear complex where Er(III) ion (shown in green) is located in the center of six equatorial oxygen donor atoms. This type of anisotropic coordination geometry is essential for Ising type magnetic anisotropy for Er(III) ion.
“Study of quantum phase transition on U-compounds”
Kyoto Univ. , Prof. K. Ishida
The U compounds occupy an important place in condensed-matter physics, since novel phenomena have been discovered, e.g.: “ferromagnetic superconductivity,” in which mutually exclusive ferromagnetism and superconductivity coexist in the same compound; “hidden order,” in which an order parameter of the ordered state has not been identified;
Prof. K. Ishida (Kyoto Univ.) performed 59Co- NMR in UCoGe and his collaborations with N. Kimura (Tohoku Univ.) was focused on the critical behavior of magnetism near the metamagnetic critical endpoint (CEP) in itinerant-magnet UCoAl by 27Al-NMR. They pointed out that the critical phenomena at the itinerant-electron MM CEP in UCoAl exhibited a common feature as a “gas- liquid” transition, from the critical exponent of Mc and Sc near the CEP[1]
[1] K. Karube, T. Hattori, S. Kitagawa, K.Ishida, N. Kimura, T. Komatsubara, Phys. Rev. B 86, 024428 (2012) Selected for Editors’ suggestion
“An application of the neputuniam series radionuclides for targeted radionuclide therapy”
Kanazawa Univ. , Assist. Prof. K. Washiyama
α-particle emitting radionuclides are gaining attention in the field of nuclear medicine. Because of their high linear energy transfer and the short range of α-particles in tissues, α-emitters (211At, 223Ra, and 225Ac) show promise in treating tumors such as leukemia, melanoma, and bone metastases.
Structure of DOTA-Re(Arg11)CCMSH labeled with an α-particle emitter, 225Ac. Recently, we labeled a peptide DOTA-Re(Arg11) CCMSH, which bound specifically to a receptor expressed in melanoma cells, with an α-emitter 225Ac.
Melanoma imaging of 111In-labeled DOTA- Re(Arg11)CCMSH in a B16F1 murine melanoma- bearing C57 mouse. Preliminary results using the γ-ray emitter 111In showed a high uptake of DOTA- Re(Arg11)CCMSH in melanoma tumors. Therapeutic studies using 225Ac are currently under- way.
"Hydrothermal synthesis for fabrication and reprocessing of MOX nuclear fuel"
Laboratory of Alpha-Ray Emitters, Asoc. Prof. T. Yamamura
An application of hydrothermal synthesis to fabrication and reprocessing of MOX fuel was focused in order to improve the nuclear fuel cycle much simpler and safer. This process enables us to reduce amounts of radioactive wastes and possible risks of fire and/or explosion, and also to control various specifications of the MOX fuel.
With a reductant, crystal of UO2 of the product is indefinite, whereas the second additive alters a fashion how the crystal grows of UO2, i.e. the shape and the size. Simultaneously, the additives govern the reductive atmosphere and determines the non-stoichiometry x of UO2+x in the range of 0.05-0.2.
"Vanadium solid-salt battery: Solid state with two redox couples"
Laboratory of Alpha-Ray Emitters, Asoc. Prof. T. Yamamura
A VSSB containing solid-composites of VOSO4/(VO2)2SO4 and VSO4/V2(SO4)3 in its positive and negative half-cells, respectively, was developed. An average EE and energy density of 87% and 77 W h kg–1, respectively, were achieved and maintained even after 2000 cycles.
Schematic of a VSSB: (1) ion exchange membrane, (2) carbon felt electrode supporting VOSO4·x4
H2O, (3) carbon felt electrode supporting V(SO4)1.5·x3H2O, (4) glassy carbon electrode.