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Sb
Kaneko, Koji; Metoki, Naoto; Kimura, Hiroyuki*; Noda, Yukio*; Matsuda, Tatsuma; Kogi, Masafumi*
Physica B; Condensed Matter, 403(5-9), p.874 - 876, 2008/04
Times Cited Count：1 Percentile：6.32(Physics, Condensed Matter)In order to clarify the detailed structure of PrOs
Sb, single crystal neutron diffraction experiments were carried out and obtained data were analyzed by means of the maximum entropy method (MEM). A space- and time-averaged nuclear density distribution reflecting a thermal vibration can be obtained through the MEM analysis. The result unveils a widely spread Pr distribution in the Sb cage at room temperature. The Pr density has a almost flat distribution in the real space centered at the Sb cage, which reaches roughly 0.58
in the full width at half maximum (FWHM). These features are far from the simple harmonic model, namely, the present result suggests the strong anharmonicity of the Pr potential in the Sb cage.
BHaga, Yoshinori; Oyamada, Akira*; Matsuda, Tatsuma; Ikeda, Shugo; Onuki, Yoshichika
Physica B; Condensed Matter, 403(5-9), p.900 - 902, 2008/04
Times Cited Count：9 Percentile：40.55(Physics, Condensed Matter)Crystal structure of a frustrated antiferomagnet UNiB was investigated precisely by the X-ray diffraction on a Czhochralski-grown high-quality single crystal. The unit cell was unambiguously determined as orthorhombic (space group Cmcm) with the lattice parameters 
= 6.97, 
= 17.14, and 
= 14.89 . These orthorhombic lattice parameters are approximately related to the reported hexagonal unit cell parameters 
and 
as = 2, = 2
and =3. They are also consistent with the previously reported weak superlattice reflections measured by the neutron scattering assuming the hexagonal lattice. We have found that four different uranium sites with the different local environment exist. Therefore UNiB can no more be regarded as a pure frustrated system as previously assumed and its magnetic properties should be reanalized based on the correct structure.
probed by muon spin rotationOishi, Kazuki; Heffner, R. H.; Ito, Takashi; Higemoto, Wataru; Morris, G. D.*; Bauer, E. D.*; Graf, M. J.*; Zhu, J.-X.*; Morales, L. A.*; Sarrao, J. L.*; et al.
Physica B; Condensed Matter, 403(5-9), p.1013 - 1014, 2008/04
Times Cited Count：0 Percentile：0(Physics, Condensed Matter)PuCoGa has attracted much interest because it is the first Pu-based superconductor, having an order of magnitude higher transition temperature 
K than the isostructural heavy fermion superconductor CeCoIn (
K). The mechanism of the superconductivity in PuCoGa is still under investigation, though recent experiments and theory suggest a magnetic origin. A unique aspect of this compound is the self-irradiation damage because Pu (
Pu, 
= 24,000 years) creates lattice defects which scatter electrons and, hence, break superconducting pairs. In order to elucidate the magnitude and temperature dependence of the magnetic penetration depth 
, we have performed 
SR measurements in the same PuCoGa single crystals after 25 and 400 days of aging. We found that 
decreased from 18.5K to 15K for the aged sample, yet a quasi-linear temperature dependence was found for the low-temperature 
in both the fresh and aged sample, consistent with 
-wave pairing symmetry. The magnitude of the muon spin relaxation rate 
in the aged sample, 
, where 
and 
are the superfluid density and the effective mass, respectively, is reduced by about 70% compared to fresh sample. This indicates that the scattering from self-irradiation induced defects is not in the limit of the conventional Abrikosov-Gor'kov pair-breaking theory, but rather in the limit of short coherence length (about 2nm in PuCoGa) superconductivity.
Hotta, Takashi
Physica B; Condensed Matter, 403(5-9), p.1371 - 1372, 2008/04
Times Cited Count：9 Percentile：40.55(Physics, Condensed Matter)We theoretically predict the Kondo effect due to geometrical degree of freedom. In an electron system coupled with dynamical Jahn-Teller impurity, the angular moment of the rotational Jahn-Teller mode with clockwise and anti-clockwise directions are screened by conduction electron orbital moment. We also predict the phonon-associated Kondo effect. It is found that the Kondo effect is significantly enhanced, when Coulomb interaction is canceled by the effective attraction mediated by Holstein phonons. We discuss possible relevance of this phenomenon to the exotic Kondo behavior observed experimentally in molecular quantum dots.
without inversion centerTateiwa, Naoyuki; Haga, Yoshinori; Ikeda, Shugo; Matsuda, Tatsuma; Yamamoto, Etsuji; Okuda, Yusuke*; Miyauchi, Yuichiro*; Settai, Rikio*; Onuki, Yoshichika*
Physica B; Condensed Matter, 403(5-9), p.1156 - 1158, 2008/04
Times Cited Count：1 Percentile：6.32(Physics, Condensed Matter)We present the result of an antiferromagnet CeIrSi without inversion center by measureing the heat capacity and the electrical resistivity of CeIrSi. Both physical quantities were measured in the same run for the same single crystal sample. A huge heat capacity anomaly was observed at the superconducting transition temperature 
= 1.6 K where the zero-resistivity was observed. The jump of the heat capacity 
is 5.7 
0.1 at 2.58 GPa. This value is the largest among previously reported superconducting materials, indicating the strong coupling superconductivity. The electronic specific heat coefficient just above is roughly estimated to be 100 20 mJ/K
mol at 2.58 GPa, which is the same as 
= 120 20 mJ/Kmol at ambient pressure.
-US
Ikeda, Shugo; Sakai, Hironori; Matsuda, Tatsuma; Tateiwa, Naoyuki; Nakamura, Akio; Yamamoto, Etsuji; Aoki, Dai*; Homma, Yoshiya*; Shiokawa, Yoshinobu*; Hedo, Masato*; et al.
Physica B; Condensed Matter, 403(5-9), p.893 - 894, 2008/04
Times Cited Count：6 Percentile：30.34(Physics, Condensed Matter)Single crystals of paramagnetic semiconductor -US with the orthorhombic (
) crystal structure were grown by chemical transport method. We measured the electrical resistivity 
under high pressure, and magnetization. With increasing pressure, the temperature dependence of approaches to semimetallic behavior and a kink anomaly appears at 
. shifts to higher temperature with increasing pressure. From the comparison with ferromagnetic semimetal UTeS having the same crystal structure, it seems that is a ferromagnetic transition.
Kato, Masaru*; Koyama, Tomio*; Machida, Masahiko; Hayashi, Masahiko*; Ebisawa, Hiromichi*; Ishida, Takekazu*
Physica B; Condensed Matter, 403(5-9), p.996 - 998, 2008/04
Times Cited Count：0 Percentile：0(Physics, Condensed Matter)Using the Bogoliubov-de Gennes equation of a tight-binding electron model with attractive on-site and nearest-neighbor sites interactions, we investigate the superconducting structure of nano-structured anisotropic superconductors. Numerical results show that nano-scaled 
/4-rotated square d-wave superconductors show various type of uperconductivities depending on the size. Especially, 
+
superconductivity, appears when size of superconductors is 10 times of coherence length.
electron system NpTGaMetoki, Naoto; Kaneko, Koji; Honda, Fuminori*; Jonen, Shintaro; Yamamoto, Etsuji; Haga, Yoshinori; Aoki, Dai*; Homma, Yoshiya*; Shiokawa, Yoshinobu*; Onuki, Yoshichika
no journal, ,
Systematic neutron scattering study revealed the diverse magnetic properties in NpTGa (T: Fe, Co, Ni, Rh, Pt) with A-, C-, G-type antiferro- and ferromagnetic and canted structure. We found that the successive magnetic transition in NpTGa (T = Fe, Ni, Rh) is an electronic transition between the high- and low-moment states. We argue that the orbital degree of freedom in the itinerant 5 compounds plays an important role for the magnetic properties. A localized model explains the ordering and phase diagram, where the quadrupole order parameter coexists with magnetic dipole in the ground state of NpTGa (T = Fe, Ni, Rh). It means that a localized model is a powerful tool to describe the static property, which is the temporal and spatial average of the fluctuating itinerant system. Our study indicates the existence of the multipole order in itinerant many body 5, where a new theoretical framework is necessary to describe these highly interesting phenomena.
Fujimori, Shinichi; Okochi, Takuo; Okane, Tetsuo; Saito, Yuji; Fujimori, Atsushi; Yamagami, Hiroshi; Ikeda, Shugo; Matsuda, Tatsuma; Haga, Yoshinori; Yamamoto, Etsuji; et al.
no journal, ,
We have observed the band structures and Fermi surfaces (FS's) of the heavy Fermion (HF) superconductors UPdAl, UNiAl and URuSi by angle-resolved photoemission experiments in soft X-ray region (SX-ARPES). SX-ARPES is a recently developed experimental technique, by which one can observe bulk-sensitive and U 5-dominant band structures and FS's of uranium compounds. We have found quasi-particle bands of U 5 electron origin form Fermi surface at low temperature, suggesting that U 5 electrons have itinerant character in these compounds. On the other hand, above 
, U 5 electrons are excluded from Fermi surface, and they become localized electrons at high temperatures. The experimental band structures and Fermi surfaces are compared with the results of band structure calculations, and the localized and itinerant natures of U 5 electrons are discussed in terms of their electronic structures.
