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Journal Articles

Nanoscale heterogeneity induced by nonmagnetic Zn dopants in the quantum critical metal CeCoIn$$_5$$; $$^{115}$$In NQR/NMR and $$^{59}$$Co NMR study

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$$_5$$ is known to be induced by slight substitutions of non-magnetic Zn atoms for In. In nominally 7% Zn substituted CeCoIn$$_5$$, an antiferromagnetic (AFM) state coexists with heavy fermion superconductivity. Heterogeneity of the electronic states is investigated in Zn doped CeCoIn$$_5$$ by means of nuclear quadrupole and magnetic resonances (NQR and NMR). Site-dependent NQR relaxation rates $$1/T_1$$ 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 $$T_{rm N}$$. At lower temperatures, an anisotropic superconducting (SC) gap below the SC transition temperature $$T_{rm c}$$, 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.

Journal Articles

Nonmagnetic-magnetic transition and magnetically ordered structure in SmS

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

 Times Cited Count:0 Percentile:0(Materials Science, Multidisciplinary)

Journal Articles

Pore distribution of compacted Ca-montmorillonite using NMR relaxometry and cryoporometry; Comparison with Na-montmorillonite

Okubo, Takahiro*; Yamazaki, Akio*; Fukatsu, Yuta; Tachi, Yukio

Microporous and Mesoporous Materials, 313, p.110841_1 - 110841_11, 2021/01

 Times Cited Count:1 Percentile:69.4(Chemistry, Applied)

Pore distributions in water-saturated Ca-montmorillonite were investigated using $$^{1}$$H NMR measurements under various dry densities (0.8 - 1.6 g/cm$$^{3}$$) and porewater salinity conditions (deionized water, 0.1 and 1 M CaCl$$_{2}$$), 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 $$T1$$ and $$T1/T2$$ 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.

Journal Articles

Enhancement of domain-wall mobility detected by NMR at the angular momentum compensation temperature

Imai, Masaki; Chudo, Hiroyuki; Matsuo, Mamoru; Maekawa, Sadamichi; Saito, Eiji

Physical Review B, 102(1), p.014407_1 - 014407_5, 2020/07

 Times Cited Count:4 Percentile:68.88(Materials Science, Multidisciplinary)

Journal Articles

Evidence for weak spin-orbit interaction experienced by Cooper pairs in the spin-triplet superconductor UPt$$_3$$; $$^{195}$$Pt-NMR study

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

 Times Cited Count:0 Percentile:0(Physics, Multidisciplinary)

Journal Articles

$$^{239}$$Pu nuclear magnetic resonance in the candidate topological insulator PuB$$_4$$

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

 Times Cited Count:2 Percentile:22.92(Materials Science, Multidisciplinary)

We present a detailed nuclear magnetic resonance (NMR) study of $$^{239}$$Pu in bulk and powdered single-crystal plutonium tetraboride (PuB$$_4$$), which has recently been investigated as a potential correlated topological insulator. The $$^{239}$$Pu NMR spectra are consistent with axial symmetry of the shift tensor showing for the first time that $$^{239}$$Pu NMR can be observed in an anisotropic environment and up to room temperature. The temperature dependence of the $$^{239}$$Pu shift, combined with a relatively long spin-lattice relaxation time ($$T_1$$), indicate that PuB$$_4$$ adopts a nonmagnetic state with gaplike behavior consistent with our density functional theory calculations. The temperature dependencies of the NMR Knight shift and $$T^{-1}$$ imply bulk gaplike behavior confirming that PuB$$_4$$ is a good candidate topological insulator.

Journal Articles

Odd-parity electronic multipolar ordering in URu$$_2$$Si$$_2$$; Conclusions from Si and Ru NMR measurements

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

AA2018-0180.pdf:1.09MB

 Times Cited Count:16 Percentile:77.41(Materials Science, Multidisciplinary)

Journal Articles

Pore distribution of water-saturated compacted clay using NMR relaxometry and freezing temperature depression; Effects of density and salt concentration

Okubo, Takahiro*; Ibaraki, Moe*; Tachi, Yukio; Iwadate, Yasuhiko*

Applied Clay Science, 123, p.148 - 155, 2016/04

 Times Cited Count:19 Percentile:73.19(Chemistry, Physical)

The pore distribution of water-saturated compacted clay (Na-montmorillonite at 0.8 and 1.4 g/cm$$^{3}$$ saturated by three salt concentrations) was evaluated using $$^{1}$$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 $$^{1}$$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 $$^{1}$$H NMR relaxometry within 10%. Correlation experiments between longitudinal ($$T_{1}$$) and transverse relation times ($$T_{2}$$) at -10$$^{circ}$$C suggested that high-mobility bulk-like water molecules existed at a clay density of 1.4 g/cm$$^{3}$$.

Journal Articles

Development status of the NMR system for the polarized $$^{3}$$He Neutron Spin Filter (NSF) in the MLF at J-PARC

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 $$^{3}$$He filter, which polarizes neutrons due to a large neutron absorption cross section of $$^{3}$$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 $$^{3}$$He nuclear spin polarization ${it P}$ 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 ${it P}$ 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 ${it P}$ monitor.

Journal Articles

Distributed twofold ordering in URu$$_2$$Si$$_2$$

Kambe, Shinsaku; Tokunaga, Yo; Sakai, Hironori; Walstedt, R. E.*

Physical Review B, 91(3), p.035111_1 - 035111_8, 2015/01

 Times Cited Count:13 Percentile:57.42(Materials Science, Multidisciplinary)

In previous $$^{29}$$Si NMR basal-plane field rotation measurements, a modest breaking of the fourfold symmetry was suggested in the hidden-order state of URu$$_2$$Si$$_2$$. Here, the angular dependence of the $$^{29}$$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.

Journal Articles

Degenerate Fermi and non-Fermi liquids near a quantum critical phase transition

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

 Times Cited Count:17 Percentile:74.1(Physics, Multidisciplinary)

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 YbRh$$_{2}$$Si$$_{2}$$. 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

Journal Articles

NMR chemical shifts of $$^{15}$$N-bearing graphene

Wang, X.*; Hou, Z.*; Ikeda, Takashi; Terakura, Kiyoyuki*

Journal of Physical Chemistry C, 118(25), p.13929 - 13935, 2014/06

 Times Cited Count:8 Percentile:32.69(Chemistry, Physical)

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 $$^{15}$$N NMR technique, in agreement with experiment. On the other hand, pyridinium-like N is hardly distinguished from pyrrole-like one because these $$^{15}$$N nuclei give nearly overlapping signals. However, our simulations suggest that $$^{1}$$H NMR is useful to discriminate between them; The NMR chemical shift of $$^{1}$$H directly bonded with pyridinium-like and pyrrole-like N is estimated as 0.8 and 10.8 ppm, respectively. The $$^{15}$$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 $$^{15}$$N NMR chemical shifts are altered sensitively by the degree of aggregation of pyridine-like $$^{15}$$N atoms both along armchair edges and at defect sites.

Journal Articles

NMR shift measurements of $$^{69}$$Ga in unconventional superconductor PuRhGa$$_{5}$$

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$$_{5}$$. PuRhGa$$_{5}$$ is a superconductor with $$T_{c}$$$$approx$$9 K, which is isomorphic to PuCoGa$$_{5}$$ with the higher $$T_{c}$$=18 K. We have reported that PuRhGa$$_{5}$$ is an unconventional superconductor with an anisotropic gap, through the measurement of NQR spin-lattice relaxation rate $$1/T_{1}$$ , while PuCoGa$$_{5}$$ is also reported to be such an anisotropic superconductor. The Knight shift $$K$$ and $$1/T_{1}$$ of NMR under applied field for the normal state of PuRhGa$$_{5}$$ 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 $$K$$ and $$1/T_{1} T$$ results. The difference between PuRhGa$$_{5}$$ and PuCoGa$$_{5}$$ will be also discussed.

Journal Articles

Multipolar phase transition in NpO$$_{2}$$; Comparison with UO$$_2$$ from $$^{17}$$O-NMR

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$$_2$$ 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$$_2$$, we have initiated the first $$^{17}$$O-NMR measurements on this system using a powder sample. From the $$^{17}$$O-NMR spectrum, the occurrence of two inequivalent oxygen sites has been confirmed below $$T_0$$= 26 K. It has also been shown that the temperature and field dependence of the $$^{17}$$O NMR spectrum can be understood by considering an unconventional hyperfine interaction between the $$^{17}$$O nuclear spins and field-induced antiferromagnetic moments arising from the longitudinal triple-$$vec{q}$$ antiferro-quadrupolar order. These NMR results give strong evidence for the occurrence of the longitudinal triple-$$vec{q}$$ multipole structure in NpO$$_2$$. We will also discuss our recent $$^{17}$$O-NMR results in a single crystal.

Journal Articles

NMR study of antiferromagnet UPtGa$$_{5}$$

Kambe, Shinsaku; Sakai, Hironori; Tokunaga, Yo; Fujimoto, Tatsuya; Kato, Harukazu; Walstedt, R. E.; Ikeda, Shugo; Matsuda, Tatsuma; Haga, Yoshinori; Onuki, Yoshichika

Journal of the Physical Society of Japan, 75(Suppl.), p.127 - 129, 2006/08

Recently, new superconductors have been discovered in Pu-based HoCoGa$$_5$$(115) structure compounds: PuCoGa$$_5$$ ($$T_{c}=18K$$) and PuRhGa$$_5$$ ($$T_{c}=9K$$). The discovery has stimulated a lot of interest in actinide compounds. We report NMR measurements on a high-quality single crystal sample of the non-superconducting U- and Np-based 115 compounds. In order to elucidate universal magnetic properties and the origin of superconductivity in the 115 families, spin-lattice relaxation and Knight shift measurements have been performed systematically in the non-superconducting 115 compounds. Comparison of dynamical properties with the superconducting Pu115 compounds will be presented.

Journal Articles

Multipolar ordering in NpO$$_2$$ probed by NMR

Tokunaga, Yo; Homma, Yoshiya*; Kambe, Shinsaku; Aoki, Dai*; Sakai, Hironori; Yamamoto, Etsuji; Nakamura, Akio; Shiokawa, Yoshinobu; Walstedt, R. E.; Yasuoka, Hiroshi

Physica B; Condensed Matter, 378-380, p.929 - 930, 2006/05

 Times Cited Count:3 Percentile:18.82(Physics, Condensed Matter)

We have initiated the first $$^{17}$$O-NMR measurements in the ordered state of NpO$$_2$$. From the $$^{17}$$O-NMR spectrum, we have confirmed the occurrence of two inequivalent oxygen sites below $$T_0$$= 26 K. It has also been shown that the $$^{17}$$O-NMR spectrum in the ordered state can be understood by considering an unconventional hyperfine interaction between the $$^{17}$$O nuclear spins and field-induced antiferromagnetic moments arising from the longitudinal triple-$$bf{q}$$ antiferro-quadrupolar order. These NMR results give strong evidence for the occurrence of the longitudinal triple-$$bf{q}$$ multipole structure in NpO$$_2$$.

Journal Articles

Unconventional superconductivity in PuRhGa$$_{5}$$; Ga NMR/NQR study

Sakai, Hironori; Tokunaga, Yo; Fujimoto, Tatsuya; Kambe, Shinsaku; Walstedt, R. E.; Yasuoka, Hiroshi; Aoki, Dai*; Homma, Yoshiya*; Yamamoto, Etsuji; Nakamura, Akio; et al.

Physica B; Condensed Matter, 378-380, p.1005 - 1006, 2006/05

 Times Cited Count:6 Percentile:32.73(Physics, Condensed Matter)

$$^{69,71}$$ Ga NMR/NQR studies have been performed on a single crystal of the transuranium superconductor PuRhGa$$_{5}$$ with $$T_{c}$$=9 K. The spin-lattice relaxation rate $$1/T_{1}$$ reveals that PuRhGa$$_{5}$$ is an unconventional superconductor having an anisotropic superconducting gap. Moreover, Korringa behavior ($$1/T_{1} T = const.$$) is observed in the normal state below 30 K. This result suggests that the superconductivity sets in after the formation of a Fermi liquid state in this compound.

Journal Articles

Ga NMR study of UGa$$_{3}$$; Antiferromagnetically ordered state

Kambe, Shinsaku; Walstedt, R. E.; Sakai, Hironori; Tokunaga, Yo; Matsuda, Tatsuma; Haga, Yoshinori; Onuki, Yoshichika

Physical Review B, 72(18), p.184437_1 - 184437_8, 2005/11

 Times Cited Count:5 Percentile:27.34(Materials Science, Multidisciplinary)

Temperature dependence of the spin-lattice relaxation time ($$T_{1}$$) at Ga site are measured for the paramagnetic and antiferromagnetically (AFM) ordered states of UGa$$_{3}$$($$T_{N}=66K$$). Clear minimaum of $$T_1$$ has been observed at $$sim62K$$ in addition to a minimun at $$T_N$$, indicating that second order phase transtion occures at both temperatures. Based on a comparison between $$T_1$$ of $$^{69}$$Ga and $$^{71}$$Ga nucleai, the enhanced fluctuations at both temparature are magnetic. The origin of the transitions are discussed.

Journal Articles

Anisotropic superconducting gap in transuranium superconductor PuRhGa$$_{5}$$; Ga NQR study on a single crystal

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, 74(6), p.1710 - 1713, 2005/06

 Times Cited Count:78 Percentile:90.85(Physics, Multidisciplinary)

$$^{69,71}$$Ga NMR/NQR studies have been performed on a single crystal of the transuranium superconductor PuRhGa$$_{5}$$ with $$T_{c}sim 9$$ K. We have observed a $$^{69}$$Ga NQR line at $$sim$$29.15 MHz, and assigned it to the $$4i$$ Ga site using the NMR results. The $$^{69}$$Ga NQR spin-lattice relaxation rate $$1/T_{1}$$ shows no coherence peak just below $$T_{rm c}$$, but obeys $$T^{3}$$ behavior below $$T_{rm c}$$. This result strongly suggests that PuRhGa$$_{5}$$ is an unconventional superconductor having an anisotropic superconducting gap. The gap amplitude 2$$Delta_{0}(Trightarrow 0)simeq5k_{rm B}T_{rm c}$$ and the residual density of states $$N_{rm res}(T=0)/N_{rm 0}(T=T_{rm c})simeq$$ 0.25 have been determined assuming a simple polar function of the form $$Delta(theta,phi)$$=$$Delta_{0}costheta$$, where $$theta$$ and $$phi$$ are angular parameters on the Fermi surface.

Journal Articles

Symmetry lowering in NpO$$_2$$; $$^{17}$$O-NMR study

Tokunaga, Yo; Homma, Yoshiya*; Kambe, Shinsaku; Aoki, Dai*; Sakai, Hironori; Yamamoto, Etsuji; Nakamura, Akio; Shiokawa, Yoshinobu; Walstedt, R. E.; Yasuoka, Hiroshi

Physica B; Condensed Matter, 359-361, p.1096 - 1098, 2005/04

 Times Cited Count:7 Percentile:35.17(Physics, Condensed Matter)

In order to elucidate the nature of the exotic ordered phase of NpO$$_2$$ below $$T_0$$= 26 K, we have initiated the first $$^{17}$$O-NMR measurements. From the temperature dependence of the $$^{17}$$O-NMR spectrum, the occurrence of two inequivalent oxygen sites has been confirmed below $$T_0$$. This finding verifies the lowering of symmetry in the ordered state of NpO$$_2$$.

113 (Records 1-20 displayed on this page)