Hideyuki Sato

Tokyo Metropolitan University, Edo, Tōkyō, Japan

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Publications (255)350.23 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: We report a study of 93Nb- and 27Al-nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) in a praseodymium based compound PrNb2Al20. The observed NMR line at around 3 T and 30 K shows a superposition of typical powder patterns of one Nb signal and at least two Al signals. 93Nb-NMR line could be reproduced by using the previously reported NQR frequency νQ ≊ 1.8MHz and asymmetry parameter η ≊ 0 [Kubo T et al 2014 JPS Conf. Proc. 3 012031]. From 27Al-NMR/NQR, NQR parameters are obtained to be νQ,A ≊ 1.53 MHz, and ηA ≊ 0.20 for the site A, and νQ,B ≊ 2.28 MHz, and ηB ≊ 0.17 for the site B. By comparing this result with the previous 27Al-NMR study of PrT2Al20 (T = Ti, V) [Tokunaga Y et al 2013 Phys. Rev. B 88 085124], these two Al site are assigned to the two of three crystallographycally inequivalent Al sites.
    Journal of Physics Conference Series 03/2015; 592:012093. DOI:10.1088/1742-6596/592/1/012093
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    ABSTRACT: We succeeded in growing a high-quality single crystal of UIr with the monoclinic PbBi-type structure by the Czochralski pulling method in a tetra-arc furnace. The magnetization measurement indicates that UIr is an Ising-like ferromagnet with the Curie temperature TC= 46 K. The magnetic moment is found.to be oriented along the [101] direction in the (010) plane. The saturated moment is 0.5 μB/U. The magnetic property, reflected in the magnetic susceptibility, electrical resistivity, Hall coefficient and thermoelectric power, is highly anisotropic. We also observed the de Haas-van Alphen (dHvA) oscillation. All the detected branches have large cyclotron effective masses ranging from 9.6 to 32 m0. They are consistent with the electronic specific heat coefficient γ=49 mJ/K2·mol.
    Journal of Nuclear Science and Technology 08/2014; 39(sup3):187-190. DOI:10.1080/00223131.2002.10875440 · 1.45 Impact Factor
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    ABSTRACT: We report the results of (121),Sb-123-nuclear quadrupole resonance (NQR) measurements on the fully filled skutterudite YbFe4Sb12 synthesized under high pressure, and compare them with those for an Yb-deficient sample synthesized under ambient pressure in order to elucidate the intrinsic behavior and the effects of the Yb-site filling fraction on magnetic properties. The NQR spectra for the fully filled sample remain narrow down to 1.5 K, indicating no sign of a phase transition, in contrast to the results of the Yb-deficient sample. The nuclear spin-lattice relaxation rate divided by temperature, 1/T1T, is composed of two terms as 1/T1T = (1/T1T)(chi) + (1/T1T)(PG). The first term (1/T1T)(chi) is scaled to the magnetic susceptibility, which is similar to the behavior of nearly ferromagnetic metals. The pseudogap behavior, related to the second term (1/T1T)(PG), is consistent with the optical conductivity measurements, and is a characteristic of the filled skutterudites with a divalent filler ion.
    Journal of the Physical Society of Japan 08/2014; 83(8):084712. DOI:10.7566/JPSJ.83.084712 · 1.48 Impact Factor
  • Proceedings of the International Conference on Strongly Correlated Electron Systems (SCES2013); 06/2014
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    ABSTRACT: We have investigated the Ru/Os concentration dependence of the Pr guest mode in Pr(Os1−xRux)4Sb12 and its variation with temperature. The Pr guest mode at ∼3.2 meV in PrOs4Sb12 at the N point linearly shifts to a higher energy with the substitution of Ru into the Os site. The energy of the Pr guest mode decreases with decreasing temperature for all compositions, indicating the presence of an anharmonic potential at the Pr site. The slope of the temperature dependence of the guest mode energy is steeper for pure PrOs4Sb12 than for the other Pr(Os1−xRux)4Sb12 compounds we measured. The present results imply the importance of the transition metal in determining anharmonicity in Pr(Os1−xRux)4Sb12
    Proceedings of the International Conference on Strongly Correlated Electron Systems (SCES2013); 06/2014
  • Proceedings of the International Conference on Strongly Correlated Electron Systems (SCES2013); 06/2014
  • Proceedings of the International Conference on Strongly Correlated Electron Systems (SCES2013); 06/2014
  • Proceedings of the International Conference on Strongly Correlated Electron Systems (SCES2013); 06/2014
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    ABSTRACT: The electronic transport, magnetic, and specific heat measurements on CeFe4As12 single crystals grown under high pressure of similar to 4 GPa have been performed, in order to clarify the reported contradictory results on the electronic state between the single crystals grown under minute pressure of similar to 4 MPa and polycrystalline samples synthesized under high pressure (similar to 4 GPa). Special emphasis was put on the huge sample dependent physical properties reported in the former, which was attributed to huge sample dependent lattice constant and morphology of grown single crystals. We found similar sample-dependent electronic transport properties also in our high pressure grown single crystals with little sample dependence of the lattice constant, suggesting that neither the lattice constant nor morphology has direct connection with the electronic properties in CeFe4As12. Based on these facts, the reason for such a sensitive sample-dependent electronic transport properties of CeFe4As12 is discussed, in correlation with the marginal Kondosemiconducting ground state of this material.
    Journal of the Physical Society of Japan 03/2014; 83(3):034710. DOI:10.7566/JPSJ.83.034710 · 1.48 Impact Factor
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    ABSTRACT: The low-temperature properties of single crystals of SmTa2Al20 have been studied by electrical resistivity, magnetization, and specific heat measurements. A lambda-type peak structure, indicating a phase transition, was found in the specific heat at T-x = 2.0 K. From an analysis of the nuclear specific heat contribution, the ordered moment is estimated to be 0.22 mu(B)/Sm, which is largely suppressed from 0.84 mu(B)/Sm for a free Sm3+ ion. The Kondo-like -log T dependence of resistivity and the suppressed effective magnetic moment of 0.09 mu(B)/Sm above T-x indicate strong c-f hybridization. The largely enhanced specific heat divided by temperature of about 3J/(mol K-2) below 0.4 K suggests the formation of extremely heavy quasiparticles in the ordered state. A notable feature commonly observed in all of these behaviors is robustness against magnetic fields. We discuss the possible relevance of multipole moments in the quartet ground state to the robustness against magnetic fields.
    Journal of the Physical Society of Japan 12/2013; 82(12):123710. DOI:10.7566/JPSJ.82.123710 · 1.48 Impact Factor
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    ABSTRACT: The low-temperature properties of NdFe4As12 single crystals grown by the As self-flux method under high pressure have been studied by magnetization, electrical resistivity, and specific heat measurements. We found that NdFe4As12 shows a ferromagnetic transition at T-c = 14.6 K. Moreover, we found additional anomalies, a shoulder in the resistivity and a Schottky-like peak in magnetic specific heat below T-c. It is rare that the corresponding peak of the specific heat is larger than the specific heat jump at T-c. From the crystal electric field analysis of Nd 4f electrons with a simple mean field approximation, we found that a model with a quasi-degenerate sextet (doublet and quartet) reproduces these anomalous features qualitatively, but quantitative differences, probably attributable to the contribution from Fe d electrons, still remain. We also found that the effective magnetic moment (4.43 mu(B)/f.u.) is larger than the Nd3+ free-ion value (3.67 mu(B)/ion), indicating the contribution of Fe itinerant magnetism.
    Journal of the Physical Society of Japan 11/2013; 82(11):114710. DOI:10.7566/JPSJ.82.114710 · 1.48 Impact Factor
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    ABSTRACT: We report the results of Sb nuclear quadrupole resonance (NQR) measurements on the filled skutterudite CeFe4Sb12 synthesized under high pressure (HP) and compare them with those for the sample synthesized under ambient pressure (AP) to understand the influence of the Ce-site filling fraction. The NQR spectra for the HP sample are much sharper than those for the AP sample, suggesting that the Ce filling fraction is higher. Also, the nuclear spin-lattice relaxation rate 1/ T 1 follows an exponential decrease 1/ T 1 ∝ exp(-Δ/ k B T), with the gap being Δ/ k B = 270 K at temperatures above 100 K, which is larger than that for the AP sample. This result suggests that the c- f hybridization is enhanced by increasing the Ce-site filling fraction.
    Journal- Korean Physical Society 08/2013; 63(3):804-808. DOI:10.3938/jkps.63.804 · 0.43 Impact Factor
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    ABSTRACT: For the unconventional heavy fermion compound SmOs4Sb12, the temperature dependence of the Sm valence state was investigated by Sm L\text{III-edge X-ray absorption spectroscopy under the application of pressure. The Sm valence was found to fluctuate up to a pressure of 3.5 GPa. From the pressure and temperature dependence of the average Sm valence, it was concluded that the Sm divalent contribution plays an important role in the heavy fermion behavior of SmOs4Sb12. Pressure dependence of a characteristic temperature in the Sm valence states exhibits a minimum at around 1 GPa. This finding demonstrates the correlation between the Sm valence and heavy fermion behavior in SmOs4Sb12.
    Journal of the Physical Society of Japan 02/2013; 82(2):3707-. DOI:10.7566/JPSJ.82.023707 · 1.48 Impact Factor
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    ABSTRACT: Ac susceptibility (χac) measurements on Pr(Os1-xRux)4Sb12 single crystals for x = 0.05 and 0.1 were performed by mutual inductance method. A peak structure caused by anomalously enhanced flux pinning force, which is so-called the peak effect, appears in the H dependence of χac. The peak structure shifts to lower fields as T increases and disappears in T > 1 K in both samples, while in PrOs4Sb12 it is observable up to near Tc. This fact indicates that the Ru substitution suppresses the peak effect. We demonstrate that the observed T dependent behavior of the peak structure can be explained roughly by the synchronization model although there remains deviation from the model curve, suggesting some modification may be needed in the model to be applied to Pr(Os1-xRux)4Sb12.
    Journal of Physics Conference Series 12/2012; 391(1):2046-. DOI:10.1088/1742-6596/391/1/012046
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    ABSTRACT: We report the results of the 121,123Sb-nuclear quadrupole resonance (NQR) measurements on the filled skutterudite RFe4Sb12 (R = La, Ce) synthesized under high pressure (HP), and compare them with those for the sample synthesized under ambient pressure (AP) in order to understand the effects of the R-site filling fraction on magnetic properties. The NQR spectra for the HP samples are much sharper than those for the AP samples, suggesting that the R-site filling fraction is high close to unity and the electronic states around Sb nuclei become uniform. In LaFe4Sb12-HP, the nuclear spin--lattice relaxation rate divided by temperature, 1/T1T, exhibits the Curie--Weiss temperature dependence 1/T1T=C/(T+θ) with the Weiss temperature θ=12 K above 30 K, indicating the development of ferromagnetic fluctuations. The magnitude of θ for the HP sample is smaller than that for the AP sample, which suggests that the system becomes close to the vicinity of ferromagnetic instability as the La-site filling fraction increases. In CeFe4Sb12-HP, 1/T1 follows the exponential decrease 1/T1 \propto \exp(-Δ/kBT) above 100 K with the gap Δ/kB of 270 K, which is larger than that for the AP sample. This result suggests that c--f hybridization is enhanced by increasing the Ce-site filling fraction.
    Journal of the Physical Society of Japan 12/2012; 81(12):4706-. DOI:10.1143/JPSJ.81.124706 · 1.48 Impact Factor
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    ABSTRACT: It has recently been found that composite multiplets are formed by the hyperfine coupling between the triplet crystalline-electric-field ground state of the 4f electrons and the 141Pr nuclear spin in Pr ions of the filled skutterudite PrRu4P12. Entropy analysis of the characteristic Schottky-type peak structure appearing in the low-temperature specific heat demonstrates that it is actually caused by thermal excitations of not only 4f electrons but also 141Pr nuclei. The hyperfine coupling constant for Pr ions in nonmetallic PrRu4P12 is determined to be A = +0.050(2) K, which is almost the same as in metallic Pr-based compounds. This fact corroborates that the intra-ion hyperfine coupling of Pr ions is independent of the type of material.
    Journal of Physics Conference Series 12/2012; 391(1):2003-. DOI:10.1088/1742-6596/391/1/012003
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    ABSTRACT: The atomic dynamics of the guest modes in heavy fermion filled skutterudites ROs4Sb12 were investigated by inelastic x-ray scattering. Comparison of the phonon dispersion relations for the filled skutterudite SmOs4Sb12 with those for the unfilled skutterudite IrSb3 indicates that the guest modes in filled skutterudites are observed as additional modes in the unfilled skutterudites. The dispersion relations for IrSb3 and SmOs4Sb12 agree reasonably well with the results obtained by ab initio calculations for IrSb3 and LaOs4Sb12, respectively. The rare-earth dependence of the inelastic x-ray scattering spectrum in the series of ROs4Sb12 compounds is difficult to interpret in terms of changes in the atomic mass and electron number of the rare-earth atom inserted into the Sb cage. The combination of inelastic x-ray scattering and x-ray absorption spectroscopy reveals a correlation between the guest mode energy and the guest free space in these compounds. The rare-earth dependence of the inelastic x-ray scattering spectrum indicates the mediation of heavy fermion behavior by the atomic motion of the guest in some ROs4Sb12 compounds and the electron-phonon coupling between the guest modes with 4f-electrons and conduction electrons in the series of ROs4Sb12 compounds.
    Physical review. B, Condensed matter 11/2012; 86(19). DOI:10.1103/PhysRevB.86.195115 · 3.66 Impact Factor
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    ABSTRACT: We report inelastic neutron scattering results for single-crystalline samples of PrFe4P12, which undergoes a transition from the heavy-electron phase to the antiferro-type nonmagnetic ordered phase. In contrast to the quasielastic magnetic response observed in the heavy electron phase, the well-defined inelastic peaks located at 1.5 and 3 meV are superimposed in the ordered phase. The maximum spectral intensity appears at the Brillouin zone center for the original Im\bar{3} structure, and the minimum spectral intensity appears at the zone boundaries including the ordering vector \mbi{q}0=(1,0,0). The evolution of the 1.5 meV peak with an applied magnetic field in the ordered phase is in agreement with excitations between 4f-electron crystalline-field-splitting levels, while the 3 meV peak is smeared out rapidly. The spectra are consistent with the recently proposed staggered ordering of a Pr site with well-localized f-electrons and that with a Kondo-singlet-like state, which are represented as the totally symmetric state accompanied by the charge modulation of carriers.
    Journal of the Physical Society of Japan 09/2012; 81(9):4711-. DOI:10.1143/JPSJ.81.094711 · 1.48 Impact Factor
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    ABSTRACT: We have investigated the electrical resistivity ρ and Hall resistivity ρH of the filled skutterudite PrFe4P12 as functions of both temperature T down to 30 mK and magnetic field H up to 17.9 T for the field directions near the [111] axis. At low temperatures, we observed a clear anomaly in ρ(H) and ρH(H) within a limited range of field directions close to H\parallel [111] at around 8 T, reflecting the onset of the high-field ordered phase (HOP) reported previously. ρ exhibits a crater like structure as a function of the field direction in the (\bar{1}10) plane with a minimum near the [111] axis. Magnetoresistance exhibits clear anomalies across the boundaries of both the low-field scalar-order phase (SOP) and the HOP. With decreasing temperature, the phase boundaries of the high-field side of the SOP and the low-field side of the HOP approach more slowly than was inferred previously. The carrier density in the HOP evaluated by the ρ and ρH measurements is more than an order of magnitude higher than that in the SOP, which rules out \mbi{q}= (0,0,1) as the ordering wave vector for the HOP. Within the HOP, we found an additional anomaly accompanied by a clear hysteresis at around 17 T below ˜0.75 K, indicating the existence of a new phase boundary. The existence of the additional state in the HOP may indicate that almost-degenerate multiple internal degrees of freedom are involved in the HOP. This finding should provide an important clue to clarify the nature and origin of the HOP.
    Journal of the Physical Society of Japan 08/2012; 81(8):4703-. DOI:10.1143/JPSJ.81.084703 · 1.48 Impact Factor
  • Journal of the Physical Society of Japan 01/2012; 81(Suppl.B):SB048. DOI:10.1143/JPSJS.81SB.SB048 · 1.48 Impact Factor

Publication Stats

3k Citations
350.23 Total Impact Points

Institutions

  • 1990–2014
    • Tokyo Metropolitan University
      • Department of Physics
      Edo, Tōkyō, Japan
  • 2007
    • Saitama University
      • Graduate School of Science and Engineering
      Saitama, Saitama, Japan
  • 2005–2007
    • The University of Tokushima
      • Faculty of Integrated Arts and Sciences
      Tokusima, Tokushima, Japan
  • 2006
    • Okayama University
      Okayama, Okayama, Japan
  • 1993–2003
    • The University of Tokyo
      Tōkyō, Japan
    • Kyoto University
      Kioto, Kyōto, Japan
  • 1995–1996
    • Osaka University
      • Department of Physics
      Suika, Ōsaka, Japan
  • 1985–1996
    • University of Tsukuba
      Tsukuba, Ibaraki, Japan
  • 1988
    • Musashi Institute of Technology
      Edo, Tōkyō, Japan