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CoSiYamauchi, Hiroki; Sari, D. P.*; Yasui, Yukio*; Sakakura, Terutoshi*; Kimura, Hiroyuki*; Nakao, Akiko*; Ohara, Takashi; Honda, Takashi*; Kodama, Katsuaki; Igawa, Naoki; et al.
Physical Review Research (Internet), 6(1), p.013144_1 - 013144_9, 2024/02
RhSiYamauchi, Hiroki; Sari, D. P.*; Watanabe, Isao*; Yasui, Yukio*; Chang, L.-J.*; Kondo, Keietsu; Ito, Takashi; Ishikado, Motoyuki*; Hagihara, Masato*; Frontzek, M. D.*; et al.
Communications Materials (Internet), 1, p.43_1 - 43_6, 2020/07
High-temperature short-range order is discovered up to 720 K in MnRhSi by complementary use of neutron scattering and muon spin relaxation measurements.
-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.*; Hagihara, 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.
-electron states in PrPdAlMetoki, Naoto; Yamauchi, Hiroki; Suzuki, Hiroyuki*; Kitazawa, Hideaki*; Hagihara, Masato*; Masuda, Takatsugu*; Aczel, A. A.*; Chi, S.*; Hong, T.*; Matsuda, Masaaki*; et al.
Journal of the Physical Society of Japan, 87(9), p.094704_1 - 094704_8, 2018/09
Times Cited Count：6 Percentile：46.54(Physics, Multidisciplinary)The -electron states of PrPdAl were revealed by neutron inelastic scattering. The flat -orbitals with large 
become stable under the two-dimensional CEF potential of unique crystal structure, which is the origin of the Ising anisotropy. A systematic understanding is possible in RPdAl based on this CEF potential. Especially the 
-type anisotropy in NpPdAl can be qualitatively understood with the positive Stevens factors. It mean that the local property is important for the physical properties of RPdAl including the heavy fermion superconductivity in NpPdAl.
Metoki, Naoto; Yamauchi, Hiroki; Matsuda, Masaaki*; Fernandez-Baca, J. A.*; Watanuki, Ryuta*; Hagihara, Masato*
Physical Review B, 97(17), p.174416_1 - 174416_10, 2018/05
Times Cited Count：6 Percentile：25.82(Materials Science, Multidisciplinary)Neutron polarization analysis has been carried out in order to clarify the magnetic structure of multiple order parameter -electron system NdB. We confirmed the non-collinear "all-in all-out" structure (
) of the in-plane moment. We found that the magnetic moment along the 
-axis 
showed diagonally antiferromagnetic structure (
). The unusual magnetic ordering is phenomenologically understood via Landau theory. We also found that a long-period incommensurate modulation of the (
) antiferromagnetic structure of with the propagation 
= (0.14, 0.14, 0.1) and 
= (0.2, 0, 0.1) in phase III and IV, respectively. It is clear that the multipole degree-of-freedom based on pseudo-quartet -electron state play important role.
Yamauchi, Hiroki; Metoki, Naoto; Watanuki, Ryuta*; Suzuki, Kazuya*; Fukazawa, Hiroshi; Chi, S.*; Fernandez-Baca, J. A.*
Journal of the Physical Society of Japan, 86(4), p.044705_1 - 044705_9, 2017/04
Times Cited Count：13 Percentile：64.28(Physics, Multidisciplinary)Neutron diffraction experiments have been carried out to characterize the magnetic structures and order parameters in an intermediate phase of NdB showing the successive phase transitions at 
K, 
K, and 
K. The observed patterns in phase II (
) are successfully explained by postulating a planar structure with static magnetic moments in the tetragonal 
-plane. We have found that the magnetic structure in phase II can be uniquely determined to be a linear combination of noncolinear "all-in/all-out"-type and "vortex"-type antiferromagnetic structures. We propose that the quadrupolar interaction holds the key to stabilizing the noncollinear magnetic structure and quadrupolar order. Here, the frustration in the Shastry - Sutherland lattice would play an essential role in suppressing the dominance of the magnetic interaction.
AlMetoki, Naoto; Yamauchi, Hiroki; Kitazawa, Hideaki*; Suzuki, Hiroyuki*; Hagihara, Masato*; Frontzek, M. D.*; Matsuda, Masaaki*; Fernandez-Baca, J. A.*
Journal of the Physical Society of Japan, 86(3), p.034710_1 - 034710_5, 2017/03
Times Cited Count：9 Percentile：56.98(Physics, Multidisciplinary)Magnetic structure of NdPdAl has been studied by means of neutron powder diffraction. We observed remarkable magnetic reflections with the modulation vector 
= (1/2 0 0) below the ordering temperature 
= 1.2 K. We found a collinear magnetic structure of Nd moment of 2.9(1) 
at 0.3 K parallel to the -axis, where the ferromagnetically ordered 
planes stack with four Nd layer period of ++-- sequence along the direction with the distance between adjuscent Nd layers to be 
. This is very similar to CePdAl with = (0.23 0.23 0) and the Ce moment parallel to the -axis. These structures with in-plane modulation 
is a consequence of the two dimensional nature of fermi surface topology in this family, coming from unique crystal structure with very long tetragonal unit cell and large distance 
7
between the rare earth layers separated by Al and two Pd layers.
Sekine, Yurina; Kobayashi, Riki*; Chi, S.*; Fernandez-Baca, J. A.*; Suzuya, Kentaro; Fujisaki, Fumika*; Ikeda, Kazutaka*; Otomo, Toshiya*; Fukazawa, Tomoko*; Yamauchi, Hiroki; et al.
JPS Conference Proceedings (Internet), 8, p.033009_1 - 033009_6, 2015/09
Neutron diffraction profiles of low-D
O-content poly-N,N,-dimethylacrylamide (PDMAA) hydrogels were measured from 100 to 300 K to investigate the structure and properties of water in hydrogels. A broad diffraction observed at temperatures lower than 220 K indicates the existence of amorphous ice in the hydrogels at low temperatures. During the heating process, diffraction peaks from ice crystals appear in the profiles. These peaks indicate that cubic ice and hexagonal ice exist at T 
220 K. We refined the structure parameters of these ices in the hydrogel, which indicate the existence of low-density ice in the hydrogel.
Sekine, Yurina; Fukazawa, Tomoko*; Aizawa, Mamoru*; Kobayashi, Riki*; Chi, S.*; Fernandez-Baca, J. A.*; Yamauchi, Hiroki; Fukazawa, Hiroshi
Journal of Physical Chemistry B, 118(47), p.13453 - 13457, 2014/08
Times Cited Count：2 Percentile：3.74(Chemistry, Physical)Neutron diffraction patterns for deuterated poly-
,,-dimethylacrylamide (PDMAA) hydrogels were measured from 10 to 300 K to investigate the structure and properties of water in the gels. Diffraction peaks observed below 250 K indicate the existence of ice in the hydrogels. Some diffraction peaks from the ice are at lower diffraction angles than those in ordinary hexagonal ice (Ih). These shifts in peaks indicate that the lattice constants of the and axes in the ice are about 0.29% and 0.3% higher than those in ice Ih, respectively. The results show that bulk low-density ice can exist in PDMAA hydrogels. The distortions in the lattice structure of ice imply significant interactions between water molecules and the surrounding polymer chains, which play an important role in the chemical and mechanical properties of the hydrogel.
Arakawa, Masashi*; Kagi, Hiroyuki; Fernandez-Baca, J. A.*; Chakoumakos, B.*; Fukazawa, Hiroshi
Geophysical Research Letters, 38, p.L16101_1 - L16101_5, 2011/08
Times Cited Count：15 Percentile：39.44(Geosciences, Multidisciplinary)The existence of ferroelectric ice XI with ordered hydrogen in space becomes of interest in astronomy and physical chemistry because of the strong electrostatic force. However, the influence was believed to be limited because it forms at narrow temperature range. From neutron diffraction experiments, we found that small hydrogen-ordered domains exist at significantly higher temperature and the domains induce the growth of "bulk" ice XI. The small ordered domain is named "memory" of hydrogen ordered ice because it is the residual structure of ice XI. Since the memory exists up to at least 111 K, most of ices in the solar system are hydrogen ordered and may have ferroelectricity. The small hydrogen-ordered domains govern the cosmochemical properties of ice and evolution of icy grains in the universe.
Fukazawa, Hiroshi; Arakawa, Masashi*; Kagi, Hiroyuki; Yamauchi, Hiroki; Chakoumakos, B. C.*; Fernandez-Baca, J. A.*
Physics and Chemistry of Ice 2010, p.421 - 428, 2011/03
Whether or not ice in the universe exists as ferroelectric is a question that has attracted interest in astrophysics and physical chemistry, because long-range electrostatic forces, caused by the ferroelectricity, might be an important factor for materials evolution and hydrogen bonding. From neutron diffraction and scattering measurements, we have studied ice with impurities, such as potassium, sodium and lithium, that acted as a catalyst. Time-resolved diffraction experiments show that ferroelectric ice XI with hydrogen-ordered arrangement nucleates and grows with time for about 5 days. We found that the doped ice that has once been converted to ice XI is a stronger ferroelectric ice than that has never been converted. We also show the existence of the ferroelectric ice under high-pressure and its formation from compressed amorphous ice.
Arakawa, Masashi*; Kagi, Hiroyuki; Fernandez-Baca, J. A.*; Chakoumakos, B. C.*; Fukazawa, Hiroshi
Physics and Chemistry of Ice 2010, p.329 - 338, 2011/03
We measured neutron diffraction profiles of KOD, NaOD, LiOD, Ca(OD), and ND
-doped ices. Ice XI, which is a hydrogen-ordered phase of normal ice (ice Ih), was observed in the KOD and NaOD-doped ices although Ca(OD) and ND-doped ice did not transformed to ice XI. The mass fraction of ice XI to that of the doped ice () was estimated using Rietveld analysis for each doped ice. The value of the doped ice, which had once experienced being ice XI, was larger than that of the doped ice, which had never experienced being ice XI. The large value of the doped ice indicates that small hydrogen-ordered domains remained above the transition temperature between ice XI and Ih. Our results suggest that large amounts of ice on icy bodies in our solar system can transform to ice XI. In this paper, we discussed the existence of the small hydrogen-ordered domains in space and the evolution of icy grain.
Fukazawa, Hiroshi; Hoshikawa, Akinori*; Chakoumakos, B. C.*; Fernandez-Baca, J. A.*
Nuclear Instruments and Methods in Physics Research A, 600(1), p.279 - 281, 2009/02
Times Cited Count：12 Percentile：62.36(Instruments & Instrumentation)We measured time-resolved neutron powder diffraction of ices doped with very small amounts of some catalysts using the wide-angle neutron diffractometer (WAND) at the High Flax Isotope Reactor (HFIR) in Oak Ridge, Tennessee. We succeeded in making ferroelectric ice, which prepared at high pressures (0.2 and 0.4 GPa), in a 60 to 75 K temperature range over tens hours. Neutron diffraction experiments confirmed the existence of a large ferroelectric structure in the sample. Therefore, thick surface (about 500 Km) of ferroelectric ice may exist on cold icy bodies, such as, Pluto and Kuiper Belt Objects (KBO). It suggests that about 70% of Pluto body is ferroelectric ice. Future telescope or planetary probe will be able to detect the huge ferroelectric-ice mass. In this symposium we report recent results at the HFIR and our future plan using higher intensity neutron beam.
Sr
CuOMatsuda, Masaaki; Fujita, Masaki*; Wakimoto, Shuichi; Fernandez-Baca, J. A.*; Tranquada, J. M.*; Yamada, Kazuyoshi*
Physical Review Letters, 101(19), p.197001_1 - 197001_4, 2008/11
Times Cited Count：48 Percentile：85.27(Physics, Multidisciplinary)We present inelastic neutron scattering experiments on a single-domain crystal of lightly-doped La
Sr
CuO. We find that the magnetic excitation spectrum in this insulating phase with a diagonal incommensurate spin modulation is remarkably similar to that in the superconducting regime, where the spin modulation is bond parallel. In particular, we find that the dispersion slope at low energy is essentially independent of doping and temperature over a significant range. The energy at which the excitations cross the commensurate antiferromagnetic wave vector increases roughly linearly with doping through the underdoped regime.
Fukazawa, Hiroshi; Hoshikawa, Akinori; Ishii, Yoshinobu; Chakoumakos, B. C.*; Fernandez-Baca, J. A.*
Astrophysical Journal, 652(1, Part2), p.L57 - L60, 2006/11
Times Cited Count：47 Percentile：72.23(Astronomy & Astrophysics)Whether ferroelectric ice, named ice XI, exists in a stable low-temperature phase attracts much interest. This question arose as a condensed-matter issue, and became of interest in astronomy (e.g., does ice XI exist on Pluto?) because astronomical observations identified the existence of crystalline ice in our solar system. From neutron diffraction experiments, we found the temperature conditions for the transformation of the largest fraction of ice into ice XI using the lowest level of impurity dopant. The finding of bulk crystal of ordered structure firmly supports that ice XI is stable. This suggests the existence of naturally occurring ice XI at a narrow temperature range (57-66 K) in our solar system.
Ye, F.*; Matsuda, Masaaki; Katano, Susumu; Yoshizawa, Hideki*; Belanger, D. P.*; Sepp
l, E. T.*; Fernandez-Baca, J. A.*; Alava, M. J.*
Journal of Magnetism and Magnetic Materials, 272-276, p.1298 - 1299, 2004/05
Times Cited Count：8 Percentile：41.01(Materials Science, Multidisciplinary)no abstracts in English
Ishii, Yoshinobu; Katano, Susumu; Suzuki, Junichi; Aizawa, Kazuya; Child, H. R.*; Morii, Yukio; Fernandez-Baca, J. A.*
Journal of the Physical Society of Japan, Vol.70, Supplement A, p.453 - 455, 2001/05
no abstracts in English
Fernandez-Baca, J. A.*; Dai, P.*; Wakabayashi, Nobuyoshi*; Plummer, E. W.*; Katano, Susumu; Tomioka, Yasuhide*; Tokura, Yoshinori*
Journal of the Physical Society of Japan, Vol.70, Supplement A, p.85 - 87, 2001/00
no abstracts in English
SrMnO(x
)Yamada, Yasusada; Suzuki, Junichi; Oikawa, Kenichi*; Katano, Susumu; Fernandez-Baca, J. A.*
Physical Review B, 62(17), p.11600 - 11608, 2000/11
Times Cited Count：38 Percentile：83(Materials Science, Multidisciplinary)no abstracts in English
Ca
MnOKatano, Susumu; Fernandez-Baca, J. A.*; Yamada, Yasusada
Physica B; Condensed Matter, 276-278, p.786 - 787, 2000/03
Times Cited Count：9 Percentile：47.89(Physics, Condensed Matter)no abstracts in English
