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-electron state of the heavy fermion superconductor NpPd
Al
and the isostructural familyMetoki, Naoto; Aczel, A. A.*; Aoki, Dai*; Chi, S.*; Fernandez-Baca, J. A.*; Griveau, J.-C.*; Hagihala, Masato*; Hong, T.*; Haga, Yoshinori; Ikeuchi, Kazuhiko*; et al.
JPS Conference Proceedings (Internet), 30, p.011123_1 - 011123_6, 2020/03
Rare earths (4) and actinides (5) provide variety of interesting states realized with competing interactions between the increasing number of electrons. Since crystal field splitting of many-body electron system is smaller than the bandwidth, (1) high resolution experiments are needed, (2) essentially no clear spectrum with well defined peaks is expected in itinerant Ce and U compounds, and (3) Np and Pu is strictly regulated. Therefore, systematic research on magnetic excitations by neutron scattering experiments of localized compounds and rare earth iso-structural reference is useful. We describe the electron states of heavy electron compounds NpPdAl and actinide and rare earth based iso-structural family.
states in UPdAl and valence crossover in the Vicinity of Heavy-Fermion superconductivityMetoki, Naoto; Haga, Yoshinori; Yamamoto, Etsuji; Matsuda, Masaaki*
Journal of the Physical Society of Japan, 87(11), p.114712_1 - 114712_9, 2018/11
Times Cited Count：2 Percentile：60.51(Physics, Multidisciplinary)The localized 5 states with 5 (
) configuration of U
ion have been revealed in UPdAl. We found that the low-lying states are the same as PrPdAl flat orbitals with large 
are stabilized by a two-dimensional CEF potential in the unique crystal structure. The present study involves the valence crossover from tetravalent to trivalent in a series of AnPdAl, demonstrated by lattice and/or transport anomaly as well as many body effects in the vicinity of the boundary. The valence instability plays important role for the unusual heavy fermion superconductivity in NpPdAl.
Ueno, Yasuhiro*; Aoki, Masaharu*; Fukao, Yoshinori*; Higashi, Yoshitaka*; Higuchi, Takashi*; Iinuma, Hiromi*; Ikedo, Yutaka*; Ishida, Keiichi*; Ito, Takashi; Iwasaki, Masahiko*; et al.
Hyperfine Interactions, 238(1), p.14_1 - 14_6, 2017/11
Times Cited Count：3 Percentile：6.53Strasser, P.*; Aoki, Masaharu*; Fukao, Yoshinori*; Higashi, Yoshitaka*; Higuchi, Takashi*; Iinuma, Hiromi*; Ikedo, Yutaka*; Ishida, Keiichi*; Ito, Takashi; Iwasaki, Masahiko*; et al.
Hyperfine Interactions, 237(1), p.124_1 - 124_9, 2016/12
Times Cited Count：5 Percentile：6.99Ito, Takanori*; Mori, Masashi*; Inukai, Manabu*; Nitani, Hiroaki*; Yamamoto, Takashi*; Miyanaga, Takashi*; Igawa, Naoki; Kitamura, Naoto*; Ishida, Naoya*; Idemoto, Yasushi*
Photon Factory News, 33(1), p.18 - 24, 2015/05
The effect of the annealing on the crystal and local structures of doped zirconia was investigated by multi-probe technique using synchrotron X-ray and neutron diffraction, and first principles calculation. It was revealed that the annealing process enhances the periodic distortion of some zirconia compounds by Rietveld/ maximum entropy methods applied to the SR-X-ray and neutron diffractions. In addition, the combined X-ray absorption spectroscopy and first-principles calculations results showed the ZrO
polyhedra in zirconia were distorted by the annealing. Those results indicate that the degradation of oxide ionic conductivity by the annealing was related to the periodic distortion in zirconia.
Ito, Takanori*; Mori, Masashi*; Inukai, Manabu*; Nitani, Hiroaki*; Yamamoto, Takashi*; Miyanaga, Takashi*; Igawa, Naoki; Kitamura, Naoto*; Ishida, Naoya*; Idemoto, Yasushi*
Journal of Physical Chemistry C, 119(16), p.8447 - 8458, 2015/04
Times Cited Count：11 Percentile：51.66(Chemistry, Physical)The effects of the annealing process on the crystal and local structures of the doped zirconia were investigated by Rietveld refinements of synchrotron X-ray and neutron diffraction, maximum entropy method (MEM), X-ray absorption spectroscopy (XAS) and first principles calculation (FPC). This study reveals that the crystal structures of the sintered and annealed ((Zr
Y
)O
and (Zr
Sc
Ce
)O) are cubic with the space 
-3
having large atomic displacement parameters (
). For the annealed (ZrY)O, the values reduce, and the electrons around the Zr/oxide ion sites gather at the center of each site. On the other hand, the annealed (ZrScCe)O shows the opposite tendency to that of the annealed (ZrY)O.
P
Araki, Shingo*; Hayashida, Minami*; Nishiumi, Naoto*; Manabe, Hiroki*; Ikeda, Yoichi*; Kobayashi, Tatsuo*; Murata, Keizo*; Inada, Yoshihiko*; Wi
niewski, P.*; Aoki, Dai*; et al.
Journal of the Physical Society of Japan, 84(2), p.024705_1 - 024705_8, 2015/02
Times Cited Count：6 Percentile：45.36(Physics, Multidisciplinary)
-USMetoki, Naoto; Sakai, Hironori; Suzuki, Michito; Yamamoto, Etsuji; Haga, Yoshinori; Matsuda, Tatsuma; Ikeda, Shugo*
JPS Conference Proceedings (Internet), 3, p.013011_1 - 013011_6, 2014/06
Uranium chalcogenides are highly interesting because of the variety of the physical properties from 5-based metal and Mott-Hibbard insulator. Especially dichalcogenide family exhibits a metal-insulator crossover depending on the chalcogenide elements, or under magnetic field and pressure. In this talk we present a recent result of our neutron scattering study on uranium dichalcogenide, which demonstrates that the metal-insulator crossover is related to the change of 5 character from localized to itinerant. The electronic structure related to this phenomenon is discussed based on the band calculation.
P under high pressureAraki, Shingo*; Hayashida, Minami*; Nishiumi, Naoto*; Manabe, Hiroki*; Ikeda, Yoichi*; Kobayashi, Tatsuo*; Murata, Keizo*; Inada, Yoshihiko*; Winiewski, P.*; Aoki, Dai*; et al.
JPS Conference Proceedings (Internet), 3, p.011081_1 - 011081_6, 2014/06
electrons with localized and itinerant charancters in -USMetoki, Naoto; Sakai, Hironori; Yamamoto, Etsuji; Haga, Yoshinori; Matsuda, Tatsuma; Ikeda, Shugo*
Journal of the Korean Physical Society, 62(12), p.1782 - 1786, 2013/06
Times Cited Count：1 Percentile：86.51(Physics, Multidisciplinary)Magnetic excitation of a narrow gap semiconductor -USwas studied by means of neutron scattering. At low temperatures clear crystalline electric field (CEF) excitations were observed, indicating localized character of 5 electrons. The excitation energy 
7 meV of the pseudo doublet state is consistent with the level scheme based on 5 configuration of U
ions, which reproduces the magnetic susceptibility, magnetization, and specific heat. With elevating temperature the conductivity recovers with 5 carriers excited beyond the gap of 90 K. Simultaneously the CEF excitation becomes weak and broad, and is replaced by a quasi-elastic response of magnetic origin, indicating the crossover of 5 character from localized to itinerant.
Hirose, Yusuke*; Yoshiuchi, Shingo*; Nishimura, Naoto*; Sakaguchi, Junya*; Enoki, Kentaro*; Iwakawa, Ken*; Miura, Yasunao*; Sugiyama, Kiyohiro*; Onuki, Yoshichika; Settai, Rikio*; et al.
Journal of the Korean Physical Society, 62(12), p.1858 - 1861, 2013/06
Times Cited Count：0 Percentile：100(Physics, Multidisciplinary)SiMetoki, Naoto; Sakai, Hironori; Yamamoto, Etsuji; Tateiwa, Naoyuki; Matsuda, Tatsuma; Haga, Yoshinori
Journal of the Physical Society of Japan, 82(5), p.055004_1 - 055004_2, 2013/05
Times Cited Count：17 Percentile：26.12(Physics, Multidisciplinary)The hidden order parameter in URuSi remains an open question for this quarter of a century. Many type of models have been proposed. The models predict unusual order parameters such as higher order multipole, dynamical origin, or very recently, "hastatic" order, accompanying Ising quasi-particles. We provide neutron scattering data measured at the wave vector 
=(003) for the in-plane magnetic component. The existence of the in-plane component in the order of 0.01 or 10
10
Bohr magneton has been proposed by a recent theoretical studies. The data were obtained also under magnetic field up to 10 T along the [010] direction in order to reveal a possible 
type antiferro-quadrupole (AFQ) order at the propagation of =(001) proposed previously. Our data indicate that there is no in-plane magnetic component within the experimental accuracy of 0.004 Bohr magneton. Namely we could not obtain the results which support these theories.
Shiga, Hideaki*; Taki, Junichi*; Washiyama, Koshin*; Yamamoto, Jumpei*; Kinase, Sakae; Okuda, Koichi*; Kinuya, Seigo*; Watanabe, Naoto*; Tonami, Hisao*; Koshida, Kichiro*; et al.
PLOS ONE (Internet), 8(2), p.e57671_1 - e57671_8, 2013/02
Times Cited Count：12 Percentile：32.23(Multidisciplinary Sciences) and CePtSiHirose, Yusuke*; Nishimura, Naoto*; Honda, Fuminori*; Sugiyama, Kiyohiro*; Hagiwara, Masayuki*; Kindo, Koichi*; Takeuchi, Tetsuya*; Yamamoto, Etsuji; Haga, Yoshinori; Matsuura, Masato*; et al.
Journal of the Physical Society of Japan, 80(2), p.024711_1 - 024711_12, 2011/02
Times Cited Count：5 Percentile：57(Physics, Multidisciplinary)Metoki, Naoto; Kaneko, Koji; Ikeda, Shugo*; Sakai, Hironori; Yamamoto, Etsuji; Haga, Yoshinori; Homma, Yoshiya*; Shiokawa, Yoshinobu*
IOP Conference Series; Materials Science and Engineering, 9, p.012088_1 - 012088_8, 2010/05
Times Cited Count：0 Percentile：100Inelastic neutron scattering study has been carried out on US. A clear crystalline electric field (CEF) peak has been observed at 7.4 meV, which is consistent with the level scheme obtained from susceptibility data assuming 5f
configuration. The CEF becomes very weak and broad, and a quasi-elastic response emerges above the characteristic temperature 100 K. It indicates the crossover of the 5f character between localized and itinerant. A quasi-elastic response can be concluded as the hybridization effect of the 5f electrons with ligand p-electrons. Our study suggests that the crossover of the 5f character is the origin of the metal-insulator transition in US.
, CeCd, and PrCd with a caged crystal structureYoshiuchi, Shingo*; Takeuchi, Tetsuya*; Oya, Masahiro*; Katayama, Keisuke*; Matsushita, Masaki*; Yoshitani, Naohisa*; Nishimura, Naoto*; Ota, Hisashi*; Tateiwa, Naoyuki; Yamamoto, Etsuji; et al.
Journal of the Physical Society of Japan, 79(4), p.044601_1 - 044601_11, 2010/04
Times Cited Count：11 Percentile：38.55(Physics, Multidisciplinary)
TEM observation of growth process of zirconium hydride in zircaloy-4 during hydrogen ion implantationShinohara, Yasunari*; Abe, Hiroaki*; Iwai, Takeo*; Sekimura, Naoto*; Kido, Toshiya*; Yamamoto, Hiroyuki; Taguchi, Tomitsugu
Journal of Nuclear Science and Technology, 46(6), p.564 - 571, 2009/06
Times Cited Count：22 Percentile：14.94(Nuclear Science & Technology) observation during hydrogen ion implantation was performed with a TEM installed in an ion accelerator to investigate the growth process of Zr hydride in Zicaloy-4. To clarify the effect of radiation damage, some samples were irradiated with 4 MeV Ni
ions prior to hydrogen implantation. Growth processes of Zr hydrides accompanying the formation of dislocations were observed. The crystallographic relationship between the Zr matrix and Zr hydrides was identical with that found in previous studies: inter- and intragranular hydrides exhibiting a tendency to grow in the 
11
0
direction. This growth can be attributed to a shear mechanism. In specimens preirradiated with Ni ions, the growth rate of hydrides was suppressed, but the growth direction was not affected by radiation defects. It was also confirmed that the black spots induced by Ni ion irradiation grew during hydrogen ion implantation, suggesting the formation of hydrides at the defects.
by neutron diffractionJonen, Shintaro; Metoki, Naoto; Yamamoto, Etsuji; Homma, Yoshiya*; Aoki, Dai*; Shiokawa, Yoshinobu*; Onuki, Yoshichika
Journal of Alloys and Compounds, 448(1-2), p.84 - 88, 2008/01
Times Cited Count：1 Percentile：85.42(Chemistry, Physical)The magnetic structure of NpPtGa
was investigated by neutron diffraction. NpPtGa exhibits an A-type antiferromagnetic structure with propagation vector 
= (0 0 1/2) below 
= 26 K. The estimated Np magnetic moment is 0.38(5) 
, and it is oriented parallel to the 
100
direction. This small moment would be consistent with the large 
= 123 mJ/(K
mol), indicative of the heavy fermion nature. The field-induced anomaly in the magnetic susceptibility is clarified to be a signature for an antiferromagnetic domain change between multi-domains to single-domain states.
Honda, Fuminori; Metoki, Naoto; Kaneko, Koji; Jonen, Shintaro; Yamamoto, Etsuji; Aoki, Dai*; Homma, Yoshiya*; Haga, Yoshinori; Shiokawa, Yoshinobu*; Onuki, Yoshichika*
Physical Review B, 74(14), p.144413_1 - 144413_12, 2006/10
Times Cited Count：19 Percentile：37.2(Materials Science, Multidisciplinary)Systematic neutron scattering experiments have been carried out in order to reveal the magnetic properties of NpNiGa. We have observed successive ferromagnetic transitions with the magnetic moment parallel to the tetragonal 
-axis at 
= 30 K and 18 K. We have also observed antiferromagnetic reflections with the propergation vector 
= [1/2 1/2 1/2], coexisting with the ferromagnetic component below 
= 18 K. Spin polarized neutron scattering experiments have revealed that only Np carries a magnetic moment. We conclude that the magnetic moments of Np atoms exhibit simple ferromagnetic ordering for 
, while a canted antiferromagnetic structure appears for . The size of the Np magnetic moment 0.78 
/Np at 3 K have been estimated. The temperature and the magnetic field dependences of these two components have also been quantitatively analyzed. (1) It is quite unusual that the Np total moment increases with the transition from the ferromagnetic to canted antiferromagnetic structure. (2) The metamagnetic transition cannot be explained in terms of a simple spin-flip mechanism with competing interactions and anisotropy. (3) Furthermore, unusual reduction of the Np magnetic moment has been accompanied by the metamagnetic transition. From these three results, we concluded that a remarkable change in the 5 electronic state was associated with the transition at and the metamagnetic transition between the ferromagnetic low-moment state and the canted antiferromagnetic high-moment state. An important role in the 5 itinerant system.
electronic transition in the itinerant antiferromagnet NpRhGaJonen, Shintaro; Metoki, Naoto; Honda, Fuminori; Kaneko, Koji; Yamamoto, Etsuji; Haga, Yoshinori; Aoki, Dai*; Homma, Yoshiya*; Shiokawa, Yoshinobu*; Onuki, Yoshichika*
Physical Review B, 74(14), p.144412_1 - 144412_8, 2006/10
Times Cited Count：25 Percentile：26.8(Materials Science, Multidisciplinary)Neutron diffraction experiments have been carried out in a single crystal of NpRhGa in order to reveal the magnetic structure and 5 electronic state of this compound. An antiferromagnetic structure with the propagation vector = (0 0 1/2) appears below 
. We found a remarkable change in the moment direction at 
, namely, the Np moment is parallel to the -axis for 
(AF1), but parallel to the 110 direction for 
(AF2). The magnitude of magnetic moment exhibits a discontinuous change at , indicating that the moment reorientation is associated with a change of the 5 electronic state. This transition might be the consequence of the competition between the magnetic and/or quadrupolar interaction in the low-moment and high-moment states. The observed magnetic form factor indicates a dominant contribution from the orbital moment, but the orbital contribution is reduced from the Np free ion state. This is consistent with the itinerant character of the 5 electrons in NpRhGa, which is revealed by dHvA experiments and band structure calculations.
