Journal of the Physical Society of Japan
Online ISSN : 1347-4073
Print ISSN : 0031-9015
ISSN-L : 0031-9015
Volume 75, Issue 9
Displaying 1-36 of 36 articles from this issue
  • Masafumi Tamura, Akiko Nakao, Reizo Kato
    2006 Volume 75 Issue 9 Pages 093701
    Published: September 15, 2006
    Released on J-STAGE: August 27, 2009
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    The temperature dependence of magnetic susceptibility, χ(T), of the P21m crystal of a novel [Pd(dmit)2] salt, (C2H5)(CH3)3P[Pd(dmit)2]2, has been measured. The observed χ(T) above 30 K is reproduced by the model of a spin-1/2 Heisenberg antiferromagnet on a triangular lattice with the exchange coupling, JkB=250 K. A phase transition at 25 K to a spin-gapped state has been found. As well as a spin-Peierls transition, this transition breaks the translational symmetry, leading to the formation of a columnar arrangement of the spin-singlet pairs. A significant role of the lattice structure in stabilizing the spin-singlet ordering is pointed out. To our knowledge, this is the first report of a two-dimensional (2D) spin system exhibiting a spin-Peierls-like transition.
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  • Munemichi Kawaguchi, Hideki Tou, Masafumi Sera, Kenichi Kojima, Tsuyos ...
    2006 Volume 75 Issue 9 Pages 093702
    Published: September 15, 2006
    Released on J-STAGE: August 27, 2009
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    121,123Sb nuclear quadrupole resonance (NQR) measurements have been performed for a polycrystalline sample of YbxFe4Sb12 with x≈0.89. Five well-separated NQR lines were observed above 18 K, which are explained by the quadrupole frequencies 121νQ=38.96 MHz, 123νQ=23.64 MHz, and the asymmetry parameter η=0.37. The NQR lines broaden after the divergence of the Sb-NQR spin lattice relaxation rate, 1⁄T1, around 18 K, which corresponds to the internal magnetic field of ∼2700 G at the Sb site. Together with magnetization measurements, the present results indicate that the electronic state in YbxFe4Sb12 (x≈0.89) changes from a paramagnetic to a ferromagnetic state at TC≈18 K.
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  • Satoshi Tsutsui, Yoshio Kobayashi, Takuya Okada, Hiromitsu Haba, Hidey ...
    2006 Volume 75 Issue 9 Pages 093703
    Published: September 15, 2006
    Released on J-STAGE: August 27, 2009
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    We have carried out X-ray absorption spectroscopy, 149Sm nuclear resonant forward scattering, and 99Ru Mössbauer spectroscopy of SmRu4P12. The X-ray absorption spectra indicate that the Sm ions are trivalent up to 14 K. The quantum beats due to magnetic dipolar ordering are observed at 4.5 K in 149Sm nuclear resonant forward scattering. The temperature dependence of time-integrated intensity in 149Sm nuclear forward scattering suggests that the magnetic dipolar ordering occurs just below the metal–insulator transition temperature. No significant changes in the parameters are observed between 77 and 5 K in 99Ru Mössbauer spectroscopy. The present result suggests a magnetic ordering accompanied by a magnetic dipole moment at the metal–insulator transition temperature in SmRu4P12 in spite of the proposal of the magnetic ordering accompanied by a Tβ-type octupole.
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  • Masaki Fujita, Masaaki Matsuda, Bjorn Fåk, Christopher D. Frost, ...
    2006 Volume 75 Issue 9 Pages 093704
    Published: September 15, 2006
    Released on J-STAGE: August 27, 2009
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    To study the detailed structure of the magnetic excitation spectrum, we performed a neutron scattering experiment on optimally electron-doped Pr0.89LaCe0.11CuO4 (Tc=25.5 K). Well-defined spin excitations existed up to an energy of ω∼180 meV, which is consistent with the recent observation by Wilson et al. [Phys. Rev. Lett. 96 (2006) 157001] for the same cuprate with a different Tc. Better statistics in our experiment revealed a more precise structure of the spectrum. As the energy increased up to ωc∼60 meV, the peak width (κ) markably increased, but in the high-energy region beyond ωc the width remained nearly independent of the energy. χ′′(ω) showed a sharp peak at ω=6 meV, which markably diminished as the energy increased until eventually a well-defined magnetic signal was not observed near ωc. However, a broad magnetic peak at (π,π) reappeared beyond ω∼100 meV. We discuss the nature of the spin excitation spectrum, which is vastly different from that of a conventional spin wave excitation with localized spins.
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  • Van An Dinh, Masayuki Toyoda, Kazunori Sato, Hiroshi Katayama-Yoshida
    2006 Volume 75 Issue 9 Pages 093705
    Published: September 15, 2006
    Released on J-STAGE: August 27, 2009
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    The prospects of half-metallic ferromagnetism being induced by the incorporation of C atoms into alkaline-earth-metal-oxides are investigated by the first principle calculation. The origin of the ferromagnetism is discussed through the calculation of the electronic structure and exchange coupling constant by using the pseudo-potential-like self-interaction-corrected local spin density method. The Curie temperature (Tc) is also predicted by employing the Monte Carlo simulation. It is shown that by taking the electron self-interaction into account, the half-metallic ferromagnetism induced by C in the host materials is more stabilized in comparison with the standard local density approximation (LDA) case, and the C’s 2p electron states in the bandgap become more localized resulting in the predominance of the short-ranged exchange interaction. While the ferromagnetism in MgO1−xCx is stabilized due to the exchange interaction of the first-nearest neighbor pairs and might be suppressed by the anti-ferromagnetic super-exchange interaction at higher x, the ferromagnetism in CaO1−xCx, SrO1−xCx, and BaO1−xCx is stabilized by both the first- and second-nearest neighbor pairs, and Tc monotonously increases with the C concentration.
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  • Duhwa Eom, Naoya Takeda, Masayasu Ishikawa
    2006 Volume 75 Issue 9 Pages 093706
    Published: September 15, 2006
    Released on J-STAGE: August 27, 2009
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    We have studied Kondo effect and quantum critical behavior in the pseudoternary system of CeCoGe3−xSix by measuring the electrical resistivity, magnetic susceptibility, and specific heat at low temperatures down to 0.05 K. Substitution of silicon for germanium generates normal chemical pressure and enhances the exchange interaction. Antiferromagnetism disappears around x∼1.2 and non-Fermi liquid-like behavior is seen, T3⁄2 or T dependence in ρ(T), depending on the temperature range and −lnT in CT. The resistivity was also measured in magnetic fields of up to 6 T and found to recover Fermi liquid behavior in magnetic fields.
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  • Hiroshi Ezawa, Toru Nakamura, Keiji Watanabe
    2006 Volume 75 Issue 9 Pages 094001
    Published: September 15, 2006
    Released on J-STAGE: August 27, 2009
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    For a given field V(x) on \\mathbbRd, we shall find (i) the exponent ν such that XT[ω]=T−ν0TV(ω(t))dt converges as T→∞ to have a non-trivial probability distribution, and (ii) the distribution itself, where ω(t) denotes the d-dimensional Ornstein–Uhlenbeck process starting from ω(0)=x at t=0. The exponent and the probability distribution are different depending on whether or not a weighted average ∫\\mathbbRdV(x)exp[−βx2⁄2D]ddx of V vanishes, where D and β are constants of the Ornstein–Uhlenbeck process. In the non-vanishing case, they are ν=1 and a Dirac delta distribution, while in the vanishing case, ν=1⁄2 and the Gaussian distribution. The results have applications to the physics of chemoreception in immune systems.
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  • Mitsusada M. Sano
    2006 Volume 75 Issue 9 Pages 094002
    Published: September 15, 2006
    Released on J-STAGE: August 27, 2009
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    Thermal conduction very far from equilibrium in ding-dong model is investigated. If we apply a large temperature difference to a small system, it exhibits non-monotone temperature profile. This astonishing behavior is explained by two-component fluid model. As a conclusion, for a small system in very far from equilibrium, the definition of temperature by the variance of momentum becomes ambiguous.
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  • R. W. Fearick, P. von Neumann-Cosel, A. Richter, S. J. Q. Robinson, L. ...
    2006 Volume 75 Issue 9 Pages 094201
    Published: September 15, 2006
    Released on J-STAGE: August 27, 2009
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    The impact of the isoscalar proton–neutron (pn) residual interaction on magnetic dipole strength distributions is investigated for the examples 46,48Ti. Shell-model calculations with different interactions are performed, where either the full set of T=0 two-body matrix elements (TBME) from the FPD6 effective interaction, a set of constant TBME, or no TBME at all are considered. The comparison with experimental data from high-resolution electron scattering reveals clear experimental signatures of the T=0 pn interaction part.
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  • Lei Tan, Cui-Ling Zhang, Jin-Fang Zhang, Xiao-Fei Zang, Ju-Ping Li
    2006 Volume 75 Issue 9 Pages 094301
    Published: September 15, 2006
    Released on J-STAGE: August 27, 2009
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    A theoretical study is carried out for the laser cooling of a moving three-level atom in a ladder configuration, driven by a bichromatic laser fields with a broad-band squeezed vacuum. The friction, diffusion coefficients and the equilibrium temperature are calculated numerically and shown graphically as a function of two-photon detunings for various cases of the squeezed vacuum. It is shown that the relative phases between the two coherent fields and the squeezed vacuum field play an important role in the cooling process. For a suitable choice of parameters, the atomic cooling temperature may be reduced to below that in the case of a vacuum, even down to two orders below the Doppler temperature limit. The efficiency of this cooling scheme is also analyzed.
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  • Jae-Tack Jeong
    2006 Volume 75 Issue 9 Pages 094401
    Published: September 15, 2006
    Released on J-STAGE: August 27, 2009
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    Two-dimensional Stokes flow through a microchannel with a slit inside composed of a couple of thin plates is investigated. At far upstream and downstream from the slit in the channel, the plane Poiseuille flow exists. The Stokes equation is solved analytically for the slip velocity boundary condition. Flow properties such as stream function and pressure distribution are determined. From the results the streamline pattern and pressure distribution are plotted, and the slip velocity at the boundaries is shown. The excess pressure drop due to the slit and the force exerted on the plate are calculated as functions of the length of the plate, and they are almost independent of the Knudsen number.
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  • Y. Okamoto
    2006 Volume 75 Issue 9 Pages 094601
    Published: September 15, 2006
    Released on J-STAGE: August 27, 2009
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    The finite temperature correction to the spin wave velocity and magnon relaxation rate are calculated in the high-field phase (HFP) of solid 3He by employing the Holstein–Primakoff 1⁄S expansion. The properties of sound are also calculated according to the methods similar to those developed by Khalatnikov et al. The anisotropy of the crystal is taken into consideration in deriving the kinetic equation as was done in the U2D2 phase. Sound velocity is obtained as a function of magnetic field and temperature. Sound attenuation resulting from magnon–magnon scattering is evaluated by collision-time approximation with a collision integral I(n) that conserves energy and momentum. The results are compared with the experimental results of Sasaki et al.
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  • A. Irizawa, A. Higashiya, S. Kasai, T. Sasabayashi, A. Shigemoto, A. S ...
    2006 Volume 75 Issue 9 Pages 094701
    Published: September 15, 2006
    Released on J-STAGE: August 27, 2009
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    Photoemission spectroscopy (PES) and O 1s X-ray absorption spectroscopy (XAS) measurements have been performed for Cd2Re2O7 single crystals. Temperature variations of their spectra reveal that the phase transition at 120 K directly changes the band structure near the Fermi level compared with another transition near 200 K. The roles of the transitions are discussed in terms of the changes in the Re–O orbital hybridization.
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  • Yoichi Nishiwaki, Hideyo Imamura, Toshiharu Mitsui, Hidekazu Tanaka, K ...
    2006 Volume 75 Issue 9 Pages 094702
    Published: September 15, 2006
    Released on J-STAGE: August 27, 2009
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    Through magnetic and dielectric measurements, a simultaneous phase transition of spin and lattice systems observed previously at 37.2 K of RbCoBr3 have been investigated by doping with nonmagnetic Mg impurities. A mutual reduction in the ferroelectric Curie temperature TC and the Néel temperature TN due to the enhancement of Mg doping confirms the occurrence of the synergistic ordering of both. A broad peak of the real part of dielectric constant along the c axis, εc(T), at approximately 32 K of the pure system splits into two sharp peaks in mixed systems. This suggests the presence of successive structural phase transitions at around this temperature. A probable sequence of crystal and magnetic structures was discussed for the successive phase transitions of RbCo1−xMgxBr3. The interplay between the spin and lattice variables of RbCoBr3 was interpreted by taking account of spin-dependent polarizability and spin-dependent spontaneous polarization. A dielectric anomaly observed at 9.0 K in RbCoBr3, where εc(T) has a sharp peak, was ascribed to the occurrence of another structural transition.
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  • Takashi Uchida, Yoshiro Kakehashi
    2006 Volume 75 Issue 9 Pages 094703
    Published: September 15, 2006
    Released on J-STAGE: August 27, 2009
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    The relative stability among the multiple spin density wave (MSDW) states in fcc transition metals has been investigated on the basis of a Ginzburg–Landau type of free energy with terms up to the fourth order in magnetic moments. Obtained magnetic phase diagrams in the space of expansion coefficients indicate the possibility of various 3Q MSDW states in fcc transition metals: the commensurate 3\\hatQ state with \\hatQ=2π⁄a (a being the lattice constant), the incommensurate linearly polarized 3Q state, and the incommensurate helically polarized 3Q state. It is shown that these 3Q states are always stabilized, when they are compared with the corresponding 2Q and 1Q states, and their magnetic moment amplitudes are the largest among those of the three states. The results are compared with previous results of the ground-state calculations, and possible scenarios to explain the experimental data of cubic γ-Fe are proposed.
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  • H. Kitano, K. Ota, A. Maeda
    2006 Volume 75 Issue 9 Pages 094704
    Published: September 15, 2006
    Released on J-STAGE: August 27, 2009
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    We report the complex microwave conductivity, σ=σ1iσ2, of Na-DNA powders, which was measured from 80 to 300 K by using a microwave cavity perturbation technique. We found that the magnitude of σ1 near room temperature was much larger than the contribution of the surrounding water molecules, and that the decrease of σ1 with decreasing temperature was sufficiently stronger than that of the conduction of counterions. These results clearly suggest that the electrical conduction of Na-DNA is intrinsically semiconductive.
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  • Takeyuki Okada
    2006 Volume 75 Issue 9 Pages 094705
    Published: September 15, 2006
    Released on J-STAGE: August 27, 2009
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    When the additively colored KCl crystals containing Li+ and Na+ ions are leaved alone at a temperature in the region of 470 to 570 K, we have found that there appear new characteristic colloid bands in the visible region. In such annealed crystals, no Tyndal cone is observed, and both the peak position and the line width of the colloid bands are almost independent of temperatures over the range of 40 K to room temperature. On the basis of analytical results of the optical absorption spectra due to colloidal particles, it is concluded that the colloid bands observed for the KCl:Li and KCl:Na crystals are attributable to the mixed alkali-metal particles consisting of Li°- and Na°-atoms and of Na°- and K°-atoms, respectively. The peak positions and the line widths of the absorption bands are discussed, together with the consideration of free-electron densities and size effects of the mixed nano-scale metal particles.
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  • Hironori Nakao, Soukichi Kodama, Kouhei Kiyoto, Youichi Murakami, Masa ...
    2006 Volume 75 Issue 9 Pages 094706
    Published: September 15, 2006
    Released on J-STAGE: August 27, 2009
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    Resonant X-ray scattering (RXS) in Y1−xCaxTiO3 has been investigated near the Y K-edge. The resonant signal has been clearly found at a forbidden reflection, (500), and the intensity shows an azimuthal angle dependence with a twofold symmetry. The RXS intensities have almost no Ca concentration dependence, although the RXS intensities at the Ti K-edge markedly decrease with increasing Ca concentration. The origin of the RXS at the Y K-edge is clarified to be the deviation from 180° of the Ti–O–Ti bond angle, namely, the tilts of the octahedra around the Y ion. We also discuss the RXS mechanism at the main edge of the Ti K-edge.
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  • Kiyohiro Sugiyama, Hiroshi Nakashima, Dai Aoki, Yoshinori Haga, Etsuji ...
    2006 Volume 75 Issue 9 Pages 094707
    Published: September 15, 2006
    Released on J-STAGE: August 27, 2009
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    We have measured the high-field magnetization for a transuranium antiferromagnet NpRhGa5 with two successive antiferromagnetic transition temperatures of TN1=36 and TN2=32 K and an ordered moment of 0.96 μB/Np. For the magnetic field along the easy-axis of the [100] direction of the tetragonal structure, the magnetization indicates a metamagnetic transition at Hc=26 T with a sharp step and saturates above Hs=38 T, with 0.43 μB/Np. On the other hand, the hard-axis magnetization for H||[001] increases linearly and saturates above Hs=28 T, with 0.44 μB/Np. These magnetization curves were discussed on the basis of reorientation and reduction of the magnetic moment.
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  • Hiroshi Miyazaki, Tomohiko Hiwasa, Masataka Oko, Isao Harada
    2006 Volume 75 Issue 9 Pages 094708
    Published: September 15, 2006
    Released on J-STAGE: August 27, 2009
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    A possible spin-reorientation transition in field-induced magnetic ordering phases of the S=1 Haldane system with large easy-plane anisotropy is proposed, using an effective Lagrangian formalism as well as the density matrix renormalization group method. Such a spin-reorientation transition is predicted in the case where the applied magnetic field is inclined from the easy axis of the anisotropy. We point out that this transition has a close connection with a variation of the order parameter even at zero temperature, although it is different from a quantum analog of the so-called spin-flop transition proposed for the system having a strong easy axis anisotropy. In connection with a novel phase observed recently in the Haldane system at high fields, we discuss possible implications for the field-induced magnetic ordering.
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  • Hiroyuki Hidaka, Hisashi Kotegawa, Satoshi Fukushima, Naoki Wada, Tats ...
    2006 Volume 75 Issue 9 Pages 094709
    Published: September 15, 2006
    Released on J-STAGE: August 27, 2009
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    We have studied the physical properties of a pressure-induced insulating phase in PrFe4P12 via Hall effect, 31P-NMR and magnetization measurements under quasi-hydrostatic pressure. In the Hall effect measurement, a decrease in the number of hole carriers due to the metal–insulator (M–I) transition is confirmed, indicating a band insulating state. The 31P-NMR spectrum exhibits abrupt broadening and the susceptibility is suppressed markedly owing to the M–I transition, suggesting that an antiferromagnetic ordering occurs in the insulating phase and the M–I transition is of first order. Both spectra corresponding to the metallic and insulating phases are observed simultaneously in a wide temperature range near the M–I transition. This fact reflects the sensitivity of the M–I transition to uniaxial stress, which is confirmed in the resistivity measurement under uniaxial stress.
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  • Yoichi Nishiwaki, Takumi Hasegawa, Kenichi Machida, Yoshio Takeuchi
    2006 Volume 75 Issue 9 Pages 094710
    Published: September 15, 2006
    Released on J-STAGE: August 27, 2009
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    In order to discuss the condensation of the K4-mode in KNiCl3-family compounds, the temperature dependences of the elastic compliances of KNiCl3, RbMnBr3, RbFeBr3, and RbCoBr3 were measured. In each compound, the temperature dependence of the elastic compliance s33 showed a sharp discontinuity at the point of structural phase transition from a prototype P63mmc structure. The structural phase transitions of the KNiCl3-family compounds are induced by the condensation of the K4-mode at the Brilluoin zone boundary in the P63mmc structure. When the K4-mode is regarded as an order parameter η, the Landau free energy includes coupling term η2T3, where T3 is an external stress. The experimental results were interpreted satisfactorily on the basis of a phenomenological Landau theory.
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  • Yoichi Asada, Tsuneya Ando
    2006 Volume 75 Issue 9 Pages 094711
    Published: September 15, 2006
    Released on J-STAGE: August 27, 2009
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    The dynamical conductivity in carbon nanotubes in the presence of impurity scattering is studied within the effective mass approximation based on an exact numerical diagonalization of the k·p Hamiltonian. By controlling the Fermi energy and the magnetic flux, the number of conducting channels at the Fermi energy Nc is varied between one, two, and three without breaking symplectic symmetry. The exact dynamical conductivity deviates significantly from that in the self-consistent Born approximation in a small frequency region corresponding to the absence of backscattering for Nc=1, the Anderson localization for Nc=2, and the presence of a perfect conducting channel for Nc=3.
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  • Junko Takahashi, Shuichi Tasaki
    2006 Volume 75 Issue 9 Pages 094712
    Published: September 15, 2006
    Released on J-STAGE: August 27, 2009
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    Electron transport through a strongly correlated quantum dot (QD) embedded in an Aharonov–Bohm (AB) ring is investigated with the aid of the finite-U slave-boson mean-field (SBMF) approach extended to nonequilibrium regime. A nonequilibrium steady state (NESS) of the mean-field Hamiltonian is constructed with the aid of the C*-algebraic approach for studying infinitely extended systems. In the linear response regime, the Fano–Kondo resonances and AB oscillations of the conductance obtained from the SBMF approach are in good agreement with the numerical renormalization group (NRG) results of Hofstetter et al. by using twice larger Coulomb interaction in the unit of the dot linewidth. At zero temperature and finite bias voltage, the resonance peaks of the differential conductance tend to split into two. At low bias voltage, the split of the asymmetric resonance can be observed as an increase of the conductance plateau. We also found that the differential conductance has zero-bias maximum or minimum depending on the background transmission via direct tunneling between the electrodes.
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  • Yoshiki Imai, Masatoshi Imada
    2006 Volume 75 Issue 9 Pages 094713
    Published: September 15, 2006
    Released on J-STAGE: August 27, 2009
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    Combining first-principles calculations with a technique for many-body problems, we investigate the properties of the transition metal oxide Sr2VO4 from the microscopic point of view. By using the local density approximation (LDA), the high-energy band structure is obtained, while screened Coulomb interactions are derived from the constrained LDA and the GW method. The renormalization of the kinetic energy is determined from the GW method. By these downfolding procedures, an effective Hamiltonian at low energies is derived. Applying the path integral renormalization group method to this Hamiltonian, we obtain ground-state properties such as the magnetic and orbital orders. Obtained results are consistent with available experimental data. We find that Sr2VO4 is close to the metal–insulator transition. Furthermore, because of the coexistence and competition of ferromagnetic and antiferromgnetic exchange interactions in this system, an antiferromagnetic and orbital-ordered state with a nontrivial and large unit cell structure is predicted in the ground state. The calculated optical conductivity shows characteristic shoulder structure in agreement with the experimental results. This suggests an orbital selective reduction of the Mott gap.
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  • Hiroko Matsuda, Keizo Endo, Masahumi Tokiyama, Hiroshi Shinmen, Yoshih ...
    2006 Volume 75 Issue 9 Pages 094714
    Published: September 15, 2006
    Released on J-STAGE: August 27, 2009
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    Measurements of transport and magnetic properties, 57Fe-Mössbauer spectroscopy and 51V-NMR were performed for a Heusler-type alloy series Fe2+xV1−xSi (0.00≤x≤0.08). In Fe2VSi (x=0.00), which had been reported to be an antiferromagnetic metal with the Néel temperature TN1=123 K, another antiferromagnetic transition was found at 34 K (TN2). The Néel temperature TN1 was found for the alloys with x less than 0.08: it decreased monotonically with increasing x. The new antiferromagnetic transition temperature TN2 was also found for x=0.02 at 64 K. The characteristic hysteresis observed in the magnetization curve below TN2 was macroscopic evidence for the occurrence of another antiferromagnetic ordering. The presence of two types of magnetic transition at ∼40 and ∼120 K for Fe2VSi was confirmed microscopically by Mössbauer spectroscopy. The Mössbauer and NMR measurements showed the presence of slight Fe/V antisite disorder, which plays an important part in the magnetic order below TN2. The magnetic structure of Fe2VSi was discussed and the idea of double antiferromagnetism was proposed.
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  • Hidekazu Mukuda, Yoshio Kitaoka, Shintaro Ishiwata, Takashi Saito, Yui ...
    2006 Volume 75 Issue 9 Pages 094715
    Published: September 15, 2006
    Released on J-STAGE: August 27, 2009
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    We report on novel magnetic and electronic properties of SrCo6O11 that exhibits a unique stepwise magnetization and its relevant magnetotransport phenomena investigated by the site-selective 59Co nuclear magnetic resonance (NMR) at zero and applied magnetic fields. This compound is composed of three Co sites in the unit cell, i.e., Co(1) in the metallic Kagomé layer, a Co(2) dimerized pillar between the layers and Co(3) in the triangular lattice. Zero-field NMR spectra have revealed that large local moments at the Co(3) sites are magnetically ordered without any trace of bulk magnetization M at zero field. The field-swept NMR spectra show that the internal hyperfine field at the Co(1) site is derived from fully polarized moments Ms at the Co(3) sites in the “1”-plateau state at fields higher than 2.5 T, whereas it is partially cancelled out in the “1/3”-plateau state in which one-third of Ms is induced at intermediate fields once a small field is applied. It has been clarified from a microscopic point of view that the local moments at Co(3) site undergo a field-induced ferrimagnetic (↑↑↓)-to-ferromagnetic (↑↑↑) transition. The Co(1) Kagomé layer and the dimerized pillar Co(2) site between the layers are of nonmagnetic origin, suggesting that the nearly quasi-2D metallic conductivity is dominated by nonmagnetic Co(1) and Co(2) sites. Consequently, unique magneto-transport phenomena observed in SrCo6O11 are demonstrated owing to the interaction between the conduction electrons at the Co(1) and Co(2) sites and the local moments at Co(3) sites.
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  • Ryo Masuda, Satoshi Higashitaniguchi, Shinji Kitao, Yasuhiro Kobayashi ...
    2006 Volume 75 Issue 9 Pages 094716
    Published: September 15, 2006
    Released on J-STAGE: August 27, 2009
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    We have observed nuclear resonant scattering of synchrotron radiation by ytterbium nuclides for the first time. The observed excited states were the second excited state of 171Yb and the first excited states of 172Yb, 174Yb, and 176Yb. The resonant energies and half-lives of these states were found to be 75.878±0.007 keV and 1.55±0.12 ns for the second excited state of 171Yb, 78.737±0.004 keV and 1.71±0.13 ns for the first excited state of 172Yb, 76.465±0.006 keV and 1.76±0.04 ns for the first excited state of 174Yb, and 82.154±0.006 keV and 1.82±0.09 ns for the first excited state of 176Yb. Nuclear resonant scattering of synchrotron radiation by ytterbium will become a new useful method for researches on materials containing ytterbium element.
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  • Om Parkash, Bhoomika Yadav, Prakash Singh, Devendra Kumar
    2006 Volume 75 Issue 9 Pages 094717
    Published: September 15, 2006
    Released on J-STAGE: August 27, 2009
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    A few compositions in the system CaCu3Ti4−xSnxO3 (0≤x≤1.0) were synthesized by solid state diffusion controlled thermochemical process. Powder X-ray diffraction patterns of all the compositions show that these compositions are single phase solid solution. All the samples have cubic crystal structure similar to undoped CaCu3Ti4O12. Microstructure shows that average grain size is about 10 μm. Dielectric measurements have been carried out in the temperature and frequency range 300–450 K and 1 kHz–1 MHz, respectively. It has been shown by complex plane impedance and modulus analysis that barrier layers form at grain boundaries in these materials. These barriers impart high value of dielectric constant to the resultant ceramic. Dielectric constant, εr can be enhanced and dielectric loss (loss tangent), D can be reduced further by chemical infiltration.
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  • Shojiro Kimura, Hirofumi Ishikawa, Yuji Inagaki, Makoto Yoshida, Susum ...
    2006 Volume 75 Issue 9 Pages 094718
    Published: September 15, 2006
    Released on J-STAGE: August 27, 2009
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    We have performed high-frequency ESR measurements on powder and aligned samples of one-dimensional quantum ferrimagnets, A3Cu3(PO4)4, with A=Sr and Ca. Large shifts of paramagnetic g-values were observed. We explain the observed g-shifts by means of an antiferromagnetic trimer model. Moreover, gradual increases of the linewidth of the ESR spectra are observed, indicating that a short-range correlation between the effective spins on the trimers begins to develop with decreasing temperature below 25 K. Analysis of the ESR signal, taking the local structures around Cu2+ ions into account, indicates quantum nature of A3Cu3(PO4)4 compounds.
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  • Youhei Yamaji, Takahiro Misawa, Masatoshi Imada
    2006 Volume 75 Issue 9 Pages 094719
    Published: September 15, 2006
    Released on J-STAGE: August 27, 2009
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    We study electron correlation effects on quantum criticalities of Lifshitz transitions at zero temperature, using the mean-field theory based on a preexisting symmetry-broken order, in two-dimensional systems. In the presence of interactions, Lifshitz transitions may become discontinuous in contrast to the continuous transition in the original proposal by Lifshitz for noninteracting systems. We focus on the quantum criticality at the endpoint of discontinuous Lifshitz transitions, which we call the marginal quantum critical point. It shows remarkable criticalities arising from its nature as a topological transition. At the point, for the canonical ensemble, the susceptibility of the order parameter χ is found to diverge as ln1⁄|δΔ| when the “neck” of the Fermi surface collapses at the van Hove singularity. More remarkably, it diverges as |δΔ|−1 when the electron/hole pocket of the Fermi surface vanishes. Here δΔ is the amplitude of the mean field measured from the Lifshitz critical point. On the other hand, for the grand canonical ensemble, the discontinuous transitions appear as the electronic phase separation and the endpoint of the phase separation is the marginal quantum critical point. Especially, when a pocket of the Fermi surface vanishes, the uniform charge compressibility κ diverges as |δn|−1, instead of χ, where δn is the electron density measured from the critical point. Accordingly, Lifshitz transition induces large fluctuations represented by diverging χ and/or κ. Such fluctuations must be involved in physics of competing orders and influence diversity of strong correlation effects.
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  • Jun-ichi Inoue, Tetsuyuki Ochiai, Kazuaki Sakoda
    2006 Volume 75 Issue 9 Pages 094720
    Published: September 15, 2006
    Released on J-STAGE: August 27, 2009
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    Spontaneous emission spectra from a single quantum dot embedded in a microcavity characterized by the quality factor (Q) are theoretically discussed in the high Q weak coupling region. It is shown that the region should be divided into two subregions in terms of the spectral shape. The spontaneous emission spectrum in one subregion has the Lorentzian line shape, which shows a cavity effect in the line width characterized by Q−1 dependence. In the other subregion, the spectral line shape is found to have a “doublet” structure, although it is in the weak coupling region. This doublet is caused by a quantum interference effect.
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  • Thang Manh Hoang, Masahiro Nakagawa
    2006 Volume 75 Issue 9 Pages 094801
    Published: September 15, 2006
    Released on J-STAGE: August 27, 2009
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    In this study, we investigate the projective-lag synchronization model of coupled multidelay feedback systems. The master synchronizes with the slave under the lag synchronization scheme and there is a scale factor between the amplitudes of state variables. The driving signal is constituted by the sum of multiple nonlinear transformations of a delayed state variable. A sufficient condition for synchronization is considered under the Krasovskii–Lyapunov theory. The effectiveness of the proposed model is demonstrated and verified by examining specific examples using modified Mackey-Glass and Ikeda systems.
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  • Takayuki Makino, Atsushi Tsukazaki, Akira Ohtomo, M. Kawasaki, Hideomi ...
    2006 Volume 75 Issue 9 Pages 095001
    Published: September 15, 2006
    Released on J-STAGE: August 27, 2009
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  • Osamu Narikiyo
    2006 Volume 75 Issue 9 Pages 095002
    Published: September 15, 2006
    Released on J-STAGE: August 27, 2009
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  • Aya Ishigaki, Tôru Moriya
    2006 Volume 75 Issue 9 Pages 098001
    Published: September 15, 2006
    Released on J-STAGE: August 27, 2009
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