Okubo, Takahiro*; Takei, Akihiro*; Tachi, Yukio; Fukatsu, Yuta; Deguchi, Kenzo*; Oki, Shinobu*; Shimizu, Tadashi*
Journal of Physical Chemistry A, 127(4), p.973 - 986, 2023/02
The identification of adsorption sites of Cs on clay minerals has been studied in the fields of environmental chemistry. The nuclear magnetic resonance (NMR) experiments allow direct observations of the local structures of adsorbed Cs. The NMR parameters of Cs, derived from solid-state NMR experiments, are sensitive to the local neighboring structures of adsorbed Cs. However, determining the Cs positions from NMR data alone is difficult. This paper describes an approach for identifying the expected atomic positions of Cs adsorbed on clay minerals by combining machine learning (ML) with experimentally observed chemical shifts. A linear ridge regression model for ML is constructed from the smooth overlap of atomic positions descriptor and gauge-including projector augmented wave (GIPAW) ab initio data. The Cs chemical shifts can be instantaneously calculated from the Cs positions on any clay layers using ML. The inverse analysis from the ML model can derive the atomic positions from experimentally observed chemical shifts.
Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Haga, Yoshinori; Tokiwa, Yoshifumi; Opletal, P.; Fujibayashi, Hiroyuki*; Kinjo, Katsuki*; Kitagawa, Shunsaku*; Ishida, Kenji*; et al.
Journal of the Physical Society of Japan, 91(2), p.023707_1 - 023707_5, 2022/02
Te NMR experiments in field () applied along the easy magnetization axis (the -axis) revealed slow electronic dynamics developing in the paramagnetic state of UTe. The observed slow fluctuations are concerned with a successive growth of long-range electronic correlations below 3040 K, where the spin susceptibility along the hard magnetization axis (the -axis) shows a broad maximum. The experiments also imply that tiny amounts of disorder or defects locally disturb the long-range electronic correlations and develop an inhomogeneous electronic state at low temperatures, leading to a low temperature upturn observed in the bulk-susceptibility in . We suggest that UTe would be located on the paramagnetic side near an electronic phase boundary, where either the magnetic or Fermi-surface instability would be the origin of the characteristic fluctuations.
NIMS Bisai Kozo Kaiseki Purattofuomu Riyo Hokokusho (Internet), 2 Pages, 2021/09
High content fly ash silica fume cement (HFSC) has been considering a candidate low alkali cements for the geological disposal of radioactive waste in Japan. JAEA has been currently performing many experiments and modeling studies relevant to validation for the long-term stability of the C-A-S-H gel which is a dominant component of the HFSC. For developing the C-A-S-H model of hydration and degradation, it is necessary to determine the composition of C-A-S-H gel and accompanied minerals when it reacts with water. In the present subject, the synthesized sample of C-A-S-H gels were analyzed by using the NMR spectra of Al and Si to determine the coordination of these element in the C-A-S-H gel.
Sakai, Hironori; Tokunaga, Yo; Kambe, Shinsaku; Zhu, J.-X.*; Ronning, F.*; Thompson, J. D.*; Ramakrishna, S. K.*; Reyes, A. P.*; Suzuki, Kohei*; Oshima, Yoshiki*; et al.
Physical Review B, 104(8), p.085106_1 - 085106_12, 2021/08
Antiferromagnetism in a prototypical quantum critical metal CeCoIn is known to be induced by slight substitutions of non-magnetic Zn atoms for In. In nominally 7% Zn substituted CeCoIn, an antiferromagnetic (AFM) state coexists with heavy fermion superconductivity. Heterogeneity of the electronic states is investigated in Zn doped CeCoIn by means of nuclear quadrupole and magnetic resonances (NQR and NMR). Site-dependent NQR relaxation rates indicate that the AFM state is locally nucleated around Zn substituents in the matrix of a heavy fermion state, and percolates through the bulk at the AFM transition temperature . At lower temperatures, an anisotropic superconducting (SC) gap below the SC transition temperature , and the SC state permeates through the AFM regions via a SC proximity effect. Applying an external magnetic field induces a spin-flop transition near 5 T, reducing the volume of the AFM regions. Consequently, a short ranged inhomogeneous AFM state survives and coexists with a paramagnetic Fermi liquid state at high fields.
Yoshida, Shogo*; Koyama, Takehide*; Yamada, Haruhiko*; Nakai, Yusuke*; Ueda, Koichi*; Mito, Takeshi*; Kitagawa, Kentaro*; Haga, Yoshinori
Physical Review B, 103(15), p.155153_1 - 155153_5, 2021/04
Nakamine, Genki*; Kinjo, Katsuki*; Kitagawa, Shunsaku*; Ishida, Kenji*; Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Nakamura, Ai*; Shimizu, Yusei*; Homma, Yoshiya*; et al.
Physical Review B, 103(10), p.L100503_1 - L100503_5, 2021/03
Okubo, Takahiro*; Yamazaki, Akio*; Fukatsu, Yuta; Tachi, Yukio
Microporous and Mesoporous Materials, 313, p.110841_1 - 110841_11, 2021/01
Pore distributions in water-saturated Ca-montmorillonite were investigated using H NMR measurements under various dry densities (0.8 - 1.6 g/cm) and porewater salinity conditions (deionized water, 0.1 and 1 M CaCl), at the temperature range of 233 - 303 K. The volume fractions of the interlayer pore including two and three hydrated layers and the non-interlayer pore in compacted Ca-montmorillonite were quantified by NMR relaxometry including and distribution analysis, and were compared with NMR cryoporometry and X-ray diffractometry. These analysis provided consistent pictures on the pore distributions in compacted Ca-montmorillonite, in contrast to Na-montmorillonite. The main factor affecting the pore distribution in compacted Ca- and Na-montmorillonite is the density, whereas the effect of porewater salinity is relatively smaller. The effect of interlayer cations is also relatively smaller at higher density, although the differences in the pore structures are significant at low density.
Imai, Masaki; Chudo, Hiroyuki; Matsuo, Mamoru; Maekawa, Sadamichi; Saito, Eiji
Physical Review B, 102(1), p.014407_1 - 014407_5, 2020/07
Lessux, G. G.*; Sakai, Hironori; Hattori, Taisuke*; Tokunaga, Yo; Kambe, Shinsaku; Kuhns, P. L.*; Reyes, A. P.*; Thompson, J. D.*; Pagliuso, P. G.*; Urbano, R. R.*
Physical Review B, 101(16), p.165111_1 - 165111_6, 2020/04
CeRhIn is a Kondo-lattice prototype in which a magnetic field 31T induces an abrupt Fermi-surface (FS) reconstruction and pronounced in-plane electrical transport anisotropy all within its antiferromagnetic state. Here we report low-temperature nuclear magnetic resonance (NMR) measurements revealing a pronounced decrease in the In formal Knight shift, without changes in crystal or magnetic structures, of CeRhIn at fields () spanning . We discuss the emergent state above in terms of a change in Ce's 4 orbitals that arises from field-induced evolution of crystal-electric field (CEF) energy levels. This change in orbital character enhances hybridization between the 4 and the conduction electrons that leads ultimately to an itinerant quantum-critical point at 50T.
Sakai, Hironori; Tokunaga, Yo; Haga, Yoshinori; Kambe, Shinsaku; Ramakrishna, S. K.*; Reyes, A. P.*; Rosa, P. F. S.*; Ronning, F.*; Thompson, J. D.*; Fisk, Z.*; et al.
JPS Conference Proceedings (Internet), 30, p.011169_1 - 011169_6, 2020/03
Uranium disulfide -US showing a semimetal-to-semiconductor crossover has been investigated by the nuclear magnetic resonance (NMR) technique for S nuclei with the nuclear spin of . Since the natural concentration 0.76% of NMR active S nuclei is too dilute, the isotopic enrichment to 50% has been carried out for the single crystal growth. The S NMR spectra have been successfully obtained using a single crystal of -US with external fields along the crystallographic axis. The S sites assignments have been made based on these NMR spectra.
Aoyama, Taisuke*; Kotegawa, Hisashi*; Kimura, Noriaki*; Yamamoto, Etsuji; Haga, Yoshinori; Onuki, Yoshichika*; To, Hideki*
Journal of the Physical Society of Japan, 88(6), p.064706_1 - 064706_7, 2019/06
Dioguardi, A. P.*; Yasuoka, Hiroshi*; Thomas, S. M.*; Sakai, Hironori; Cary, S. K.*; Kozimor, S. A.*; Albrecht-Schmitt, T. E.*; Choi, H. C.*; Zhu, J.-X.*; Thompson, J. D.*; et al.
Physical Review B, 99(3), p.035104_1 - 035104_6, 2019/01
We present a detailed nuclear magnetic resonance (NMR) study of Pu in bulk and powdered single-crystal plutonium tetraboride (PuB), which has recently been investigated as a potential correlated topological insulator. The Pu NMR spectra are consistent with axial symmetry of the shift tensor showing for the first time that Pu NMR can be observed in an anisotropic environment and up to room temperature. The temperature dependence of the Pu shift, combined with a relatively long spin-lattice relaxation time (), indicate that PuB adopts a nonmagnetic state with gaplike behavior consistent with our density functional theory calculations. The temperature dependencies of the NMR Knight shift and imply bulk gaplike behavior confirming that PuB is a good candidate topological insulator.
Kambe, Shinsaku; Tokunaga, Yo; Sakai, Hironori; Hattori, Taisuke; Higa, Nonoka; Matsuda, Tatsuma*; Haga, Yoshinori; Walstedt, R. E.*; Harima, Hisatomo*
Physical Review B, 97(23), p.235142_1 - 235142_10, 2018/06
Okubo, Takahiro*; Ibaraki, Moe*; Tachi, Yukio; Iwadate, Yasuhiko*
Applied Clay Science, 123, p.148 - 155, 2016/04
The pore distribution of water-saturated compacted clay (Na-montmorillonite at 0.8 and 1.4 g/cm saturated by three salt concentrations) was evaluated using H NMR relaxometry and freezing point depression. The populations of interlayer water with four hydrated state and non-interlayer water were calculated from the assumed thresholds. The sample with lower density exhibits higher population of non-interlayer water up to 55%. Low-temperature H NMR experiments in view of freezing point depression indicated that mesopore water in approximately 4 nm space observed in the calorimetric study was considered as non-interlayer water and the threshold temperature. The result showed that population of non-interlayer water by expected from freezing point depression agreed with H NMR relaxometry within 10%. Correlation experiments between longitudinal () and transverse relation times () at -10C suggested that high-mobility bulk-like water molecules existed at a clay density of 1.4 g/cm.
Sakai, Kenji; Oku, Takayuki; Hayashida, Hirotoshi*; Kira, Hiroshi*; Hiroi, Kosuke; Ino, Takashi*; Oyama, Kenji*; Okawara, Manabu*; Kakurai, Kazuhisa; Shinohara, Takenao; et al.
JPS Conference Proceedings (Internet), 8, p.036015_1 - 036015_6, 2015/09
The polarized He filter, which polarizes neutrons due to a large neutron absorption cross section of He with strong spin selectivity, becomes a convenient neutron spin filter (NSF) because it is operated immediately after its installation in beam lines without any neutron beam adjustments. For realizing such the NSF, a nuclear magnetic resonance (NMR) system is indispensable for monitoring He nuclear spin polarization of the NSF. We have developed the flexible NMR system based on adiabatic fast passage (AFP) and pulse NMR methods by using their complementary features. In comparing with the values of obtained by neutron transmission measurement at the beam line 10 of the J-PARC, we measured the correlations between the AFP and pulse NMR signals as changing condition of temperature, amplitude and applying period of the radio frequency field for the pulse NMR, and so on. As the results, we confirmed that our system would function enough as the monitor.
Kambe, Shinsaku; Tokunaga, Yo; Sakai, Hironori; Walstedt, R. E.*
Physical Review B, 91(3), p.035111_1 - 035111_8, 2015/01
In previous Si NMR basal-plane field rotation measurements, a modest breaking of the fourfold symmetry was suggested in the hidden-order state of URuSi. Here, the angular dependence of the Si NMR linewidth is analyzed in detail, indicating the occurrence of a distribution of twofold local fields at the Si sites even in a high-quality single crystal. The relation between sample quality and the occurrence of effects having twofold symmetry is discussed.
Kambe, Shinsaku; Sakai, Hironori; Tokunaga, Yo; Lapertot, G.*; Matsuda, Tatsuma*; Knebel, G.*; Flouquet, J.*; Walstedt, R. E.*
Nature Physics, 10(11), p.840 - 844, 2014/11
In new observations reported here, we find that coexisting, static Fermi liquid and non-Fermi liquid states are a key feature of the QCPT in YbRhSi. By means of nuclear magnetic resonance (NMR) spin-lattice relaxation time measurements on a single crystal sample, it is revealed that the FL and NFL states are invariant,while their relative proportion in a crossover is field dependent near the QCPT. Such a pair of states has remained hidden in Ce compounds, owing presumably to short lifetimes for the two states. A new scaling law for the occupation ratio of the two states is derived, and could be widely applicable to Kondo-lattice systems
Wang, X.*; Hou, Z.*; Ikeda, Takashi; Terakura, Kiyoyuki*
Journal of Physical Chemistry C, 118(25), p.13929 - 13935, 2014/06
The NMR chemical shifts of possible N-containing moieties at edges and defects of graphene are investigated by using the first-principles method. Our computations show that pyridine-like and graphite-like N are rather easily identifiable using N NMR technique, in agreement with experiment. On the other hand, pyridinium-like N is hardly distinguished from pyrrole-like one because these N nuclei give nearly overlapping signals. However, our simulations suggest that H NMR is useful to discriminate between them; The NMR chemical shift of H directly bonded with pyridinium-like and pyrrole-like N is estimated as 0.8 and 10.8 ppm, respectively. The N NMR signals for various moieties at edges we considered are found to be similar to the corresponding ones at defects except for pyridine-like nitrogens. Conversely, the N NMR chemical shifts are altered sensitively by the degree of aggregation of pyridine-like N atoms both along armchair edges and at defect sites.
Sakai, Hironori; Tokunaga, Yo; Fujimoto, Tatsuya; Kambe, Shinsaku; Walstedt, R. E.; Yasuoka, Hiroshi; Aoki, Dai*; Homma, Yoshiya*; Yamamoto, Etsuji; Nakamura, Akio; et al.
Journal of the Physical Society of Japan, 75(Suppl.), p.50 - 52, 2006/08
Very recently, we have succeeded in NMR/NQR measurements for PuRhGa. PuRhGa is a superconductor with 9 K, which is isomorphic to PuCoGa with the higher =18 K. We have reported that PuRhGa is an unconventional superconductor with an anisotropic gap, through the measurement of NQR spin-lattice relaxation rate , while PuCoGa is also reported to be such an anisotropic superconductor. The Knight shift and of NMR under applied field for the normal state of PuRhGa suggest an anisotropic feature of hyperfine and/or spin fluctuation in this system. We will outline the superconducting state and report the nature of the normal state based on the basis of and results. The difference between PuRhGa and PuCoGa will be also discussed.
Tokunaga, Yo; Homma, Yoshiya*; Kambe, Shinsaku; Aoki, Dai*; Ikushima, Kenji; Sakai, Hironori; Ikeda, Shugo; Yamamoto, Etsuji; Nakamura, Akio; Shiokawa, Yoshinobu; et al.
Journal of the Physical Society of Japan, 75(Suppl.), p.33 - 35, 2006/08
The low-temperature phase transition in NpO has attracted much attention as a promising candidate for a new class of phase transitions associated with octupolar degrees of freedom. In order to elucidate the nature of this exotic phase transition in NpO, we have initiated the first O-NMR measurements on this system using a powder sample. From the O-NMR spectrum, the occurrence of two inequivalent oxygen sites has been confirmed below = 26 K. It has also been shown that the temperature and field dependence of the O NMR spectrum can be understood by considering an unconventional hyperfine interaction between the O nuclear spins and field-induced antiferromagnetic moments arising from the longitudinal triple- antiferro-quadrupolar order. These NMR results give strong evidence for the occurrence of the longitudinal triple- multipole structure in NpO. We will also discuss our recent O-NMR results in a single crystal.