Refine your search:     
Report No.
 - 
Search Results: Records 1-20 displayed on this page of 76

Presentation/Publication Type

Initialising ...

Refine

Journal/Book Title

Initialising ...

Meeting title

Initialising ...

First Author

Initialising ...

Keyword

Initialising ...

Language

Initialising ...

Publication Year

Initialising ...

Held year of conference

Initialising ...

Save select records

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

Ruderman-Kittel interaction between Si in URu$$_{2}$$Si$$_{2}$$

Kambe, Shinsaku; Hattori, Taisuke; Tokunaga, Yo; Sakai, Hironori; Matsuda, Tatsuma*; Haga, Yoshinori; Walstedt, R. E.*

Journal of Physics; Conference Series, 969(1), p.012033_1 - 012033_6, 2018/03

 Times Cited Count:1 Percentile:64.34

High quality URu$$_{2}$$Si$$_{2}$$ enriched in $$^{29}$$Si isotope, which is an NMR nucleus, by 52% was prepared. Since the natural abundance ratio of $$^{29}$$Si isotope is about 4%, the accumulated measurement time can be shortened to about one hundredth by this concentration. Results of the Si-NMR linewidth of hidden ordered phase using this single crystal sample have already been reported. In this report, we will report more detailed analysis on the magnetic field, temperature and angle of this line width We also discuss the possibility of distribution of magnetic susceptibility in two-fold symmetry by RKKY model.

Journal Articles

Nature of distributed two-fold ordering in URu$$_2$$Si$$_2$$

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

Journal of Physics; Conference Series, 868(1), p.012003_1 - 012003_7, 2017/07

BB2015-1834.pdf:0.47MB

 Times Cited Count:0 Percentile:0.04

In the hidden-ordered state of URu$$_2$$Si$$_2$$, a modest breaking of the fourfold symmetry was suggested in previous $$^{29}$$Si NMR basal-plane field rotation measurements. Based on the detail analysis of $$^{29}$$Si NMR linewidth, the occurrence of a distribution of twofold local fields at the Si sites is suggested even in a high-quality single crystal. A possible picture for the distributed two-fold ordering will be discussed.

Journal Articles

$$T$$ dependence of nuclear spin-echo decay at low temperatures in YbRh$$_2$$Si$$_2$$

Kambe, Shinsaku; Sakai, Hironori; Tokunaga, Yo; Hattori, Taisuke; Lapertot, G.*; Matsuda, Tatsuma*; Knebel, G.*; Flouquet, J.*; Walstedt, R. E.*

Physical Review B, 95(19), p.195121_1 - 195121_8, 2017/05

AA2017-0083.pdf:0.74MB

 Times Cited Count:3 Percentile:23.04(Materials Science, Multidisciplinary)

The authors report $$^{29}$$Si nuclear spin-echo oscillations and decay measurements on a single crystal of YbRh$$_2$$Si$$_2$$. These quantities are found to be $$T$$ independent from 300 K down to $$sim$$20 K, showing, however, a strong $$T$$ dependence below 20 K. These results indicate that electronic states near the Fermi level are modified at low temperatures. The observed spin-echo oscillations can be interpreted with the Ruderman-Kittel and pseudo-dipolar interactions between nearest-neighbor Si nuclei driven by conduction electron scattering at the Fermi surface. Possible modifications to the Fermi surface at low temperatures are discussed.

Journal Articles

$$^{29}$$Si NMR spin-echo decay in YbRh$$_2$$Si$$_2$$

Kambe, Shinsaku; Sakai, Hironori; Tokunaga, Yo; Hattori, Taisuke; Lapertot, G.*; Matsuda, Tatsuma*; Knebel, G.*; Flouquet, J.*; Walstedt, R. E.*

Journal of Physics; Conference Series, 683(1), p.012006_1 - 012006_7, 2016/02

BB2015-1546.pdf:0.87MB

 Times Cited Count:1 Percentile:60.83

By means of nuclear magnetic resonance (NMR) spin-lattice relaxation time ($$T_1$$) measurements on a single crystal sample YbRh$$_2$$Si$$_2$$, the magnetic excitations around quantum critical phase transition is investigated. It is revealed that the coexisting Fermi and non-Fermi states appears near the quantum critical phase transition. Such a mottled state is considered to have remained hidden in Ce and U heavy fermion compounds, owing presumably to short lifetimes for the two states. The mottled state is highly anisotropic to applied magnetic field, which is consistent with previous studies. The origin of mottled state will be discussed.

Journal Articles

Dilute RKKY model for NMR line broadening in the hidden-order state of URu$$_2$$Si$$_2$$

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

Physical Review B, 93(4), p.045122_1 - 045122_8, 2016/01

 Times Cited Count:5 Percentile:32.3(Materials Science, Multidisciplinary)

A well-known analytic model for Lorentzian broadening of metallic NMR lines by dilute localized magnetic centers embedded in a lattice has been applied to the case of the twofold-symmetry magnetism in URu$$_2$$Si$$_2$$. The observed Lorentzian spectra are accounted for with a simple formula giving the $$^{29}$$Si NMR linewidth in terms of the susceptibility of the magnetic broadening centers and a Ruderman-Kittel-Kasuya-Yosida (RKKY) coupling parameter.

Journal Articles

Anisotropic magnetic fluctuations in YbRh$$_2$$Si$$_2$$

Kambe, Shinsaku; Sakai, Hironori; Tokunaga, Yo; Lapertot, G.*; Matsuda, Tatsuma*; Knebel, G.*; Flouquet, J.*; Walstedt, R. E.*

Journal of Physics; Conference Series, 592(1), p.012085_1 - 012085_5, 2015/03

 Times Cited Count:2 Percentile:65.76

Recently there is renewed interest in quantum critical phase transitions (QCPT) at $$T=0$$ K in metallic strongly-correlated electron systems. From early experimental results, the QCPT in the Kondo-lattice compound YbRh$$_2$$Si$$_2$$ is not a case of the ordinary spin density wave (SDW) instability observed in Ce-based Kondo-lattices, but a candidate for a novel locally critical case In new observations reported here, we find that coexisting, static Fermi liquid (FL) and non-Fermi liquid (NFL) states are a key feature of the QCPT in YbRh$$_2$$Si$$_2$$. 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

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

Self-radiation effects and glassy nature of magnetic transition in AmO$$_2$$ revealed by $$^{17}$$O-NMR

Tokunaga, Yo; Nishi, Tsuyoshi; Nakada, Masami; Ito, Akinori*; Sakai, Hironori; Kambe, Shinsaku; Homma, Yoshiya*; Honda, Fuminori*; Aoki, Dai*; Walstedt, R. E.*

Physical Review B, 89(21), p.214416_1 - 214416_8, 2014/06

 Times Cited Count:7 Percentile:36.72(Materials Science, Multidisciplinary)

The magnetic phase transition near $$T_0=8.5$$ K in AmO$$_2$$ has been investigated microscopically by means of $$^{17}$$O NMR. To avoid complexities arising from sample aging associated with the alpha decay of $$^{243}$$Am, all measurements have been performed within 40 days after sample synthesis. Even during such a short period, however, a rapid change of NMR line shape has been observed at 1.5 K, suggesting that the ground state of AmO$$_2$$ is very sensitive to disorder. We have also confirmed the loss of $$^{17}$$O NMR signal intensity over a wide temperature range below $$T_0$$, and more than half of oxygen nuclei are undetectable at 1.5 K. This behavior reveals the persistence of slow and distributed spin fluctuations down to temperatures well below $$T_0$$. In the paramagnetic state, strong NMR line broadening and spatially inhomogeneous spin fluctuations have been observed. The results are all indicative of short-range, spin-glass-like character for the magnetic transition in this system.

Journal Articles

Anisotropic energy scale for degenerate Fermi and non-Fermi liquids near a quantum critical phase transition in YbRh$$_2$$Si$$_2$$

Kambe, Shinsaku; Sakai, Hironori; Tokunaga, Yo; Lapertot, G.*; Matsuda, Tatsuma*; Knebel, G.*; Flouquet, J.*; Walstedt, R. E.*

Physical Review B, 91(16), p.161110_1 - 161110_5, 2014/04

 Times Cited Count:3 Percentile:17.86(Materials Science, Multidisciplinary)

Based on $$^{29}$$Si nuclear spin-lattice relaxation time ($$T_1$$) data on a single crystal of YbRh$$_2$$Si$$_2$$, the coexisting Fermi liquid (FL) and non-Fermi liquid (NFL) states around the quantum critical phase transition have been found to be sensitive to the direction of the applied magnetic field. Augmented scaling analysis shows that the anisotropic characteristic temperature and field are roughly 10 times larger for $$Hparallel c$$ than for $$Hparallel a$$, consistent with a previously obtained anisotropic phase diagram.

Journal Articles

NMR study of in-plane twofold ordering in URu$$_2$$Si$$_2$$

Kambe, Shinsaku; Tokunaga, Yo; Sakai, Hironori; Matsuda, Tatsuma*; Haga, Yoshinori; Fisk, Z.; Walstedt, R. E.*

Physical Review Letters, 110(24), p.246406_1 - 246406_5, 2013/06

 Times Cited Count:42 Percentile:87.82(Physics, Multidisciplinary)

We report $$^{29}$$Si NMR spectra and Knight shift measurements as a function of applied field orientation in the (001) basal plane of URu$$_2$$Si$$_2$$. Observed linewidth oscillations confirm the in-plane 2-fold ordered domain state observed in recent magnetic susceptibility measurements. Analysis of our linewidth data leads to the estimate $$sim0.4%$$ for the 2-fold intrinsic (mono-domain) susceptibility anisotropy in the basal plane, a value $$sim15$$ times smaller than that obtained from recent susceptibility measurements.

Journal Articles

$$^{237}$$Np nuclear relaxation rate in heavy fermion superconductor NpPd$$_5$$ Al$$_2$$

Chudo, Hiroyuki; Tokunaga, Yo; Kambe, Shinsaku; Sakai, Hironori; Haga, Yoshinori; Matsuda, Tatsuma; Onuki, Yoshichika; Yasuoka, Hiroshi; Aoki, Dai*; Homma, Yoshiya*; et al.

Physical Review B, 84(9), p.094402_1 - 094402_5, 2011/09

 Times Cited Count:6 Percentile:31.79(Materials Science, Multidisciplinary)

Journal Articles

T-dependent nuclear hyperfine coupling at the In site in CeIrIn$$_{5}$$

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

Journal of the Physical Society of Japan, 80(Suppl.A), p.SA009_1 - SA009_3, 2011/07

We report an $$^{115}$$In NMR study of a single-crystal sample of the heavy fermion superconductor CeIrIn$$_5$$. The observed non-linear variation of Knight Shift with static susceptibility in the normal state is consistent with the two-fluid (components) model of Nakatsuji et al, indicating that two individual contributions to static susceptibility exist. However, our results can also be understood in terms of a T-dependent hyperfine coupling, which accounts for the spin-lattice relaxation data naturally on the basis of a one-component dynamical susceptibility. In addition, the observed T-dependence of the hyperfine coupling is scaled to a density of states given by dynamical mean field theory (DMFT). We believe that this contrast between the static and dynamical properties is a crucial dual nature of the heavy fermion crossover, which related with the coherence between localized and itinerant excitations.

Journal Articles

Quantum critical behavior in heavy-fermion superconductor CeIrIn$$_5$$

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

Physical Review B, 82(14), p.144503_1 - 144503_7, 2010/10

 Times Cited Count:14 Percentile:55.9(Materials Science, Multidisciplinary)

Based on analysis of nuclear ($$^{115}$$In) spin-lattice relaxation time measurements on the heavy fermion superconductor CeIrIn$$_5$$, $$vec{q}$$, $$w$$, and temperature-dependences of the dynamical susceptibility Im$$chi(vec{q},omega_n)$$ near the antiferromagnetic wave vector $$vec{Q}$$ at low energy $$omega_n sim 10^{-4}$$ meV have been estimated. The $$T$$-dependences found, Im$$chi(vec{Q},omega_n) sim T^{-3/2}$$ and antiferromagnetic correlation length $$xisim T^{-3/4}$$, are consistent with quantum critical behavior for a three dimensional antiferromagnet ($$d$$=3, $$z$$=2) having a spin density wave instability.

Journal Articles

La substitution effect and hyperfine-enhanced $$^{141}$$Pr nuclear spin dynamics in PrPb$$_3$$; $$^{139}$$La NMR study in Pr$$_{0.97}$$La$$_{0.03}$$Pb$$_3$$

Tokunaga, Yo; Sakai, Hironori; Chudo, Hiroyuki; Kambe, Shinsaku; Yasuoka, Hiroshi; Suzuki, Hiroyuki*; Walstedt, R. E.*; Homma, Yoshiya*; Aoki, Dai*; Shiokawa, Yoshinobu*

Physical Review B, 82(10), p.104401_1 - 104401_6, 2010/09

 Times Cited Count:5 Percentile:28.15(Materials Science, Multidisciplinary)

$$^{139}$$La NMR studies have been performed on PrPb$$_3$$ substituted with 3% La. The temperature dependence of the local magnetic susceptibility around La ions has been extracted from the $$^{139}$$La Knight shift. These data show that the non-magnetic $$Gamma_3$$ crystalline-electric-field (CEF) ground state (GS) is preserved even at the nearest neighboring Pr ions, although their CEF level scheme is slightly modified due to the La substitution. On the other hand, the temperature dependence of the nuclear spin-lattice relaxation rate $$1/T_1$$ is found to be well reproduced by assuming the same CEF level scheme over a wide temperature range. However, $$1/T_1$$ shows a strong upturn below 10 K, which is not expected from the non-magnetic CEF GS. We show that the low temperature anomaly can be quantitatively understood in terms of a cross-relaxation process between $$^{141}$$Pr and $$^{139}$$La nuclear spins.

Journal Articles

One-component description of magnetic excitations in the heavy-fermion compound CeIrIn$$_{5}$$

Kambe, Shinsaku; Tokunaga, Yo; Sakai, Hironori; Chudo, Hiroyuki; Haga, Yoshinori; Matsuda, Tatsuma; Walstedt, R. E.*

Physical Review B, 81(14), p.140405_1 - 140405_4, 2010/04

 Times Cited Count:19 Percentile:64.83(Materials Science, Multidisciplinary)

We report an $$^{115}$$In NMR study of a single-crystal sample of the heavy fermion compound CeIrIn$$_5$$. The observed non-linear variation of Knight shift with static susceptibility is consistent with the two-fluid model of Nakatsuji $textit{et al}$. However, our results can also be understood in terms of a $$T$$-dependent hyperfine coupling, which accounts for the spin-lattice relaxation data naturally on the basis of a one-component dynamical susceptibility. In addition, the observed $$T$$-dependence of the hyperfine coupling is scaled to a density of states given by dynamical mean field theory.

Journal Articles

Diagnosis of quantum criticality by nuclear spin-echo decay method

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

Physica Status Solidi (B), 247(3), p.520 - 524, 2010/03

 Times Cited Count:2 Percentile:13.13(Physics, Condensed Matter)

In order to diagnose the quantum critical behaviour in heavy fermion systems, the Gaussian spin-spin relaxation time $$T_{2G}$$ determined by NMR spin-echo decay measurements is found to be useful. Combined with the spin-lattice relaxation time $$T_1$$, an exponent $$phi$$ of quantity $$T_1T/T_{2G}^2 sim T^{phi}$$ is predicted to be sensitive to the type of quantum criticality. In fact in heavy fermion USn$$_3$$ near the quantum critical point, $$T_1T/T_{2G}^2$$ is found to be constant as expected for the $$3D$$-SDW magnetic instability.

Journal Articles

Quantum criticality in a uranium heavy fermion system revealed with NMR spin-spin relaxation

Kambe, Shinsaku; Sakai, Hironori; Tokunaga, Yo; Matsuda, Tatsuma; Haga, Yoshinori; Yasuoka, Hiroshi; Chudo, Hiroyuki; Walstedt, R. E.*

Journal of Physics; Conference Series, 200, p.012076_1 - 012076_4, 2010/02

 Times Cited Count:1 Percentile:49.66

In order to clarify quantum criticality in heavy fermion systems, we propose to use the Gaussian spin-echo decay rate $$1/T_{2G}$$ of the NMR spin-spin relaxation. In contrast to the spin-lattice relaxation rate $$1/T_1$$, which is connected with the dynamical susceptibility Im$$chi(q,omega)$$, $$1/T_{2G}$$ is driven by the static susceptibility Re$$chi(q,0)$$ at finite $$q$$ for an antiferromagnet. The combined quantity $$T_1T/T_{2G}^2$$ is found to provide key information in determining the nature of quantum criticality. The $$T$$-dependence of $$T_1T/T_{2G}^2$$ for the Sn site in the heavy fermion compound USn$$_3$$ is presented as an example.

Journal Articles

Crossover from the quantum critical to overdamped regime in the heavy-fermion system USn$$_3$$

Kambe, Shinsaku; Sakai, Hironori; Tokunaga, Yo; Matsuda, Tatsuma; Haga, Yoshinori; Chudo, Hiroyuki; Walstedt, R. E.*

Physical Review Letters, 102(3), p.037208_1 - 037208_4, 2009/01

 Times Cited Count:6 Percentile:43.51(Physics, Multidisciplinary)

We report measurements of the $$^{119}$$Sn nuclear spin echo decay rate $$1/T_{2G}$$ in the heavy fermion compound USn$$_3$$. From $$1/T_{2G}$$, the magnetic spin-spin correlation length $$xi$$ is found to vary as $$xisim T^{-3/4}$$ above $$sim$$ 100 K, which is expected for a quantum critical regime at high temperatures. Combined with the spin-lattice relaxation rate $$1/T_1$$, $$T_1T/T_{2G}^2$$ is found to be temperature independent in the heavy fermion state below $$T^* sim$$ 30 K. This indicates that the heavy fermion state of USn$$_3$$ is categorized in the overdamped regime with a dynamical critical exponent $$z=2$$. These observations are consistent with a spin density wave (SDW) magnetic instability at the quantum critical point.

76 (Records 1-20 displayed on this page)