Journal of the Physical Society of Japan
Online ISSN : 1347-4073
Print ISSN : 0031-9015
ISSN-L : 0031-9015
Volume 67, Issue 3
Displaying 1-50 of 59 articles from this issue
  • Yosuke Watanabe, Masayoshi Tajiri
    Subject area: Mathematical methods in physics.
    1998 Volume 67 Issue 3 Pages 705-708
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    The two y-periodic solitons solution(i.e. the arrays of the localized structure in the y-direction) to the Davey-Stewartson I equation is analyzed to show that the soliton resonance exists between them. There are two types of singular interactions: one is the resonant interaction where two y-periodic solitons interact so as to make a new y-periodic soliton while the other is the extremely long-range interaction where two solitons interchange with each other, infinitely apart.
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  • Hidetsugu Sakaguchi
    Subject area: Statistical physics and thermodynamics.
    1998 Volume 67 Issue 3 Pages 709-712
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    A Langevin equation is proposed to perform a simulation for the Feynman ratchet model. A stochastic boundary condition is introduced for the role of a pawl in the Feynman ratchet model.The mathematical model can be solved using the Fokker-Planckequation. The solution is compared with the Langevin simulation.A coupled system of the ratchet elements exhibits smooth unidirectional motion when the coupling constant is large.
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  • Hiroyoshi Naito, Masayoshi Todorokihara, Yoichi Hirose, Ou–Yang ...
    Subject area: Structure of liquids and solids; crystallography.
    1998 Volume 67 Issue 3 Pages 713-716
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    Electric field-induced polygonal deformation of smectic-A toroidal domains in isotropic phase has been observed in the binary mixtures of octyloxycyanobiphenyl with dodecyl alcohol. It is found that the number of sides of polygonally deformed smectic-A domains (m) is increased with increasing electric field, and that at a constant electric field larger smectic-A domainspossess higher values of m. These experimental findings can successfully be explained in terms of numerical solutions to the variation problem for equilibrium shapes of smectic-A phase in isotropic phase [H. Naito, M. Okuda and Z. Ou-Yang:Phys. Rev. Lett. 70 (1993) 2912].
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  • Masaaki Nakamura
    Subject area: Electron states in condensed matter.
    1998 Volume 67 Issue 3 Pages 717-720
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    The spin-gap phase of the one-dimensional t-J-J' model is studied by the level-crossing of the singlet and the triplet excitation spectra. The phase boundary obtained between the Tomonaga-Luttinger and the spin-gap phases is remarkably consistent with the analytical results at the J, J'→ 0 and the low-density limits discussed by Ogata et al. The spin-gap phase has a single domain in the phase diagram even if the spin gap opens at half-filling. The phase boundary coincides with the Kρ=1 line where the Tomonaga-Luttinger liquid behaves as free electrons, in the low-density region. The relation between our method and the solution of the two-electron problem is also discussed.
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  • Naoki Nakamura, Yoshikazu Suzumura
    Subject area: Electron states in condensed matter.
    1998 Volume 67 Issue 3 Pages 721-724
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    The response function, χRSDW(q, ω), of 2 kF-SDW (spin density wave) with momentum 2 kF+q and frequency ω has been studied for the Tomonaga-Luttinger model by taking account of the momentum cutoff of the repulsive interaction where kF is the Fermi momentum. We have found that Im, χRSDW(q, ω) as a function of ω exhibits a novel peak located at an energy with the Fermi velocity, in addition to two peaks at energies with the renormalized velocities, vρ and vσ corresponding to charge and spin excitations. Temperature dependence of Im, χRSDW(q, ω) is calculated to show that the spin fluctuation is dominant at low temperatures for the strong interaction and that the peak vanishes at high temperatures leading to a crossover into that in the absence of interaction.
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  • Nobuhito Kokubo, Takahisa Terashima, Satoshi Okuma
    Subject area: Electronic transport in condensed matter.
    1998 Volume 67 Issue 3 Pages 725-728
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    The voltage noise SV(f) in a thick amorphous MoxSi1-x film is studied over a broad frequency range spanning six decades (f=0.1, Hz--100, kHz) in magnetic fields just above and below the melting field, as a function of a steady current. The origin of the low-frequency (f≈ 0.1--10, Hz) noise observed near the zero-resistance region is mainly due to temperature fluctuations and the contribution due to flux motion is very small. In contrast, SV(f) at higher frequencies (f≈ 10, Hz--100, kHz) appears to be dominated by the flux motion. These results are compared with recent experiments on YBa2Cu3O7-δ films.
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  • Takahide Yamaguchi, Ryuta Yagi, Shun–ichi Kobayashi, Youiti Ootu ...
    Subject area: Electronic transport in condensed matter.
    1998 Volume 67 Issue 3 Pages 729-731
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    We investigated the transport properties of two-dimensional arrays of small Josephson junctions of which a number of junctions are removed. We found that the more the number of removed junctions, the more rapidly the array resistance increases with decreasing temperature. The enhancement of the temperature dependence of resistance is larger than that expected from the difference in the creation energy of charge and anti-charge solitons on two adjacent electrodes. This indicates that low-temperature conductance of the arrays depends on the strength of the Coulomb interaction between charges.
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  • Minoru Suzuki, Shin–ichi Karimoto, Kazuichi Namekawa
    Subject area: Superconductivity.
    1998 Volume 67 Issue 3 Pages 732-735
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    We report on interlayer tunneling spectroscopyusing very thin stacks of intrinsic Josephsonjunctions fabricated on the surface of a Bi2Sr2CaCu2O8 single crystal. It is found that a pseudogap evolves below 180 K and continuesto exist below Tc. It is also found that thesuperconducting gap evolves below Tcwithin the pseudogap. As a consequence of thisfinding, it is shown that the semiconductivec-axis resistivity can be interpreted in a straightforward mannerin terms of the pseudogap and thatthe tunneling resistance is temperature independent.
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  • Hiroshi Shimahara
    Subject area: Superconductivity.
    1998 Volume 67 Issue 3 Pages 736-739
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    Nonuniform superconducting state due to strong spin magnetism is studied in two-dimensional (2D) type-II superconductors near the second order phase transition line between the normal and superconducting states. The optimum spatial structure of the order parameter is examined in systems with cylindrically symmetric Fermi surfaces. It is found that states with 2D structures have lower free energies than the traditional one-dimensional solutions, at low temperatures and high magnetic fields. For s-wave pairing, triangular, square, and hexagonal states are favored depending on the temperature, while square states are favored at low temperatures for d-wave pairing. In these states, the order parameters have 2D structures such as square and triangular lattices.
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  • Masaki Azuma, Mikio Takano, Roger S. Eccleston
    Subject area: Magnetic properties and materials.
    1998 Volume 67 Issue 3 Pages 740-743
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    An inelastic neutron scattering study was performed on a Zn-substituted spin-1/2 Heisenberg 2-leg ladder compound Sr(Cu1-xZnx)2O3 (x ≤ 0.04) to investigate nonmagnetic impurity effects on the quantum spin system with a large spin gap of approximately --400 K. The magnitude of the spin gap was found to be independent of Zn concentration, 33 meV, while the integrated magnetic scattering, which corresponds to the singlet-triplet excitation, decreased monotonically with increasing x.On account of the total-sum rule, this result supports the existence of a finite in-gap density of states at E = 0, which was suggested from the T-linear magnetic specific heat.
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  • Tomoyuki Yosihama, Masakazu Nishi, Kenji Nakajima, Kazuhisa Kakurai, Y ...
    Subject area: Magnetic properties and materials.
    1998 Volume 67 Issue 3 Pages 744-747
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    Inelastic neutron scattering measurement of NaV2O5 singlecrystal samples was carriedout to measure their magnetic excitations in the spin-Peierls dimerizedstate. We found a steep dispersion along the b*-axis (chaindirection), having a spin-Peierls gap of almost 10 meV at (3, 0.5, 0). Along the a*-axis (interchain direction), two excitation modeswith a weak dispersion have been observed. In addition, a novel intensitymodulation has been discovered along this direction, which has not been expected fromthe crystal structure reported so far.
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  • Akihiro Tanaka, Masahiko Machida
    Subject area: Magnetic properties and materials.
    1998 Volume 67 Issue 3 Pages 748-751
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    We critically examine the issue raised by Nagaosa and Oshikawa [J. Phys. Soc. Jpn. 65 (1996) 2241] on how Fujikawa's Jacobian arising from chiral anomaly contributes a topological term to the derivative expansion of the 1d Hubbard model at half filling, thus governing the behaviour of the spin gap. We find that when the nonabelian nature of the system is properly accounted for, the scheme requires modification. The modified result is shown to agree with nonabelian bosonization. Extensions to spin-Peierls systems are outlined.
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  • Tetsuya Kato, Ken–ichi Takatsu, Hidekazu Tanaka, Wakako Shiramur ...
    Subject area: Magnetic properties and materials.
    1998 Volume 67 Issue 3 Pages 752-754
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    Single-crystal neutron inelastic scattering was performed in order to investigate the magnetic excitations of KCuCl_3, which has a singlet ground state with an excitation gap. The constant-Q energy scan profiles are collected at T=8 K for selected reciprocal points in the a&star--c&star plane which includes the double-chain direction (a-axis). Dispersion relations along the a&star- and c&star-axes are determined. It is suggested that the present system can be magnetically described as a coupled antiferromagnetic dimer system rather than a double spin chain. The lowest excitation energy is determined to be 2.70 meV at Q=(0, 0, -1) and (1, 0, ± 1), the value of which is consistent with our previous evaluation of the excitation gap from the high-field magnetization measurement.
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  • Masahiko Isobe, Yutaka Ueda, Kohichi Takizawa, Tsuneaki Goto
    Subject area: Magnetic properties and materials.
    1998 Volume 67 Issue 3 Pages 755-758
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    Powder samples of MgV2O5, which has a structure similar to a spin ladder compound CaV2O5, were synthesized and the magnetic properties were investigated. The magnetic susceptibility shows a broad maximum around 100, K and below about 15, K, it decreases more rapidly with decreasing temperature. The magnetization curves in high fields up to 17, T at 1.5, K and 30, T at 1.7, K show a change of slope around Hc-- 12.5, T, which can be considered to be a transition from a singlet ground state to a gapless magnetic state. The excitation gap {Δ} is evaluated as {Δ}/kB-- 17, K in agreement with the energy gap of about 2, meV from the inelastic neutron scattering. The results strongly suggest that MgV2O5 is a spin ladder system with a spin gap.
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  • Atsushi Goto, Tadashi Shimizu, Haruyoshi Aoki, Masaki Kato, Kazuyoshi ...
    Subject area: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
    1998 Volume 67 Issue 3 Pages 759-762
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    Anisotropies of the spin-lattice relaxation rates (1/T_1) at the Cu(1)sites of YBa2Cu3O7 and YBa2Cu4O8 were examined usingthe NMR/NQR methods. The anisotropy data enabled us to infer approximateq-dependences and anisotropies of the form factors (Fα(q_y), α=a, b, c) at Cu(1). We found that the anisotropies in YBa2Cu3O7 are explainable only in terms of the hyperfine fields withina single chain, while these hyperfine fields do not account foranisotropies in YBa2Cu4O8. As a possible explanation for thesituation in YBa2Cu4O8, effects of the transferred hyperfinefields from the other chain of the double Cu-O chains are discussed.
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  • Shigeaki Wada, Hisao Hayakawa
    Subject area: Other areas of research of general interest to physicists.
    1998 Volume 67 Issue 3 Pages 763-766
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    The traffic jam in a fluid model of traffic flow proposed byKerner and Konhäuser [Phys. Rev. E 52 (1995) 5574]is analyzed.An analytic scaled kink solution which characterizestraffic-jam formation is presented.The validity of the solution has been confirmed throughcomparison with the results of the simulation of the model.
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  • Mohammad Iqbal
    Subject area: Mathematical methods in physics.
    1998 Volume 67 Issue 3 Pages 767-771
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    In this paper we have converted the Laplace transform into Fredholm integral equation of the first kind of convolution type, which is an ill-posed problem and used maximum likelihood regularization method to solve it. The method is applied to various test examples taken from the literature. The method gives a good approximation to the true solution and compares well with maximum entropy23) and other regularization32) methods. Our results confirm that our method is competitive with other recently presented methods. The results are shown in the table and the diagrams.
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  • Xing–Biao Hu, Robin Bullough
    Subject area: Mathematical methods in physics.
    1998 Volume 67 Issue 3 Pages 772-777
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    In this paper, the Caudrey-Dodd-Gibbon-Kotera-Sawada hierarchy in bilinear form is considered. A Bäcklund transformation for the CDGKS hierarchy is presented. Under certain conditions, the corresponding nonlinear superposition formula is proved.
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  • Zuonong Zhu, Hongci Huang
    Subject area: Mathematical methods in physics.
    1998 Volume 67 Issue 3 Pages 778-783
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    A new Lax integrable hierarchy associated with a properly spectral problem is obtained. Using the trance identity method, the Hamiltonian form of the proposed Lax hierarchy is also given.
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  • Tomohiro Sasamoto, Miki Wadati
    Subject area: Mathematical methods in physics.
    1998 Volume 67 Issue 3 Pages 784-790
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    The similarity between the asymmetric simple exclusion process (ASEP)and a derivative nonlinear Schrödinger (DNLS) type model is discussed.Using the Bethe ansatz, the determinant representation for thesolution of the Schrödinger equation is obtained for the DNLS type model with a special value of the coupling constant.
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  • Akira Nakamura
    Subject area: Mathematical methods in physics.
    1998 Volume 67 Issue 3 Pages 791-798
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    We have obtained explicit N-soliton solutions of the 1+1 dimensional Toda Molecule (=finite Toda) equation. It has been shown that for the properly chosen values of arbitrary constant parameters and the large molecule limit, the present solutions actually represent patterns having running peaks namely soliton solutions.
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  • Toshihiro Tanizawa
    Subject area: Classical and quantum physics: mechanics and fields.
    1998 Volume 67 Issue 3 Pages 799-815
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    The quantum tunneling rate through an inverted parabolapotential in an oscillating external field is studied.The tunneling rate is calculated within quasi-classical accuracyas a function of the frequency of the field.In this calculation, the complex-time path integral method, which has been previously appliedto the case of tunneling through static potentials, is used after being appropriately extendedfor application to the case of tunneling through explicitlytime-dependent potentials.Since the Feynman kernel for the case consideredin the present paper can be exactly obtained, we are able to calculate the tunneling rateover a considerably wider range of frequenciesof the oscillating field than in the case thatthis quantity is calculated through a perturbativetreatment of the external field, as done in the previous studies.The present analysis reveals that the perturbative analysis for thepresent problem is insufficient even in the region whereit has been considered to be appropriate.From the numerical calculation of the quasi-classical tunneling rate, we find that, as the frequency of the external field increases, all of the tunneling rates are initially enhancedby a significant amount, but beyond a certain value, all tunneling rates become rapidly decaying functions of this frequency.This fact may imply that the consideration beyond quasi-classicalaccuracy is needed in the high frequency regime.Tunneling processes that do not conserve energy are also considered.They cannot be neglected in this time-dependent problem, and we find that tunneling rates become large when tunneling particles acquireenergy during tunneling.
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  • Seizo Watarai, Seiji Miyashita
    Subject area: Statistical physics and thermodynamics.
    1998 Volume 67 Issue 3 Pages 816-824
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    Critical properties of the two successive phase transitionsof Ising-like Heisenberg antiferromagnets on the hexagonal latticeare examined by the Monte Carlo method.In order to obtain the critical exponents, the finite size scaling methods areused for the lattice sizes of L=18 -- 48. Using the reweighting Monte Carlo method, the exponents at the higher critical temperature are estimated as 1/ν=1.481±0.019 andγ/ν=1.980±0.016, which agree with those of the 3DXY model.At the lower critical temperature, standard procedure of the reweighting methoddoes not give values of the exponents with satisfactory precision.Thus we estimate the exponents carefully with aid of the ordinary Monte Carlo method at various temperatures near Tc.The values of 1/ν ~= 1.48±0.006 and γ/ν ~=1.97±0.050 are obtained and we conclude that those are consistent with the universality class of the 3DXY model.
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  • Pham Hong Son, Kenkichi Ohba
    Subject area: Fluid dynamics.
    1998 Volume 67 Issue 3 Pages 825-832
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    A linear theory of electrohydrodynamic instability of a perfectly conducting liquid jet injected from a capillary tube which is raised to a high DC voltage is presented. The effects of electric field strength and its configuration, jet velocity and physical properties of fluids are considered in the derived equation for disturbance growth rate. It is shown that the jet instability is sensitive to the electric field strength. The axisymmetric mode of instability is dominant at low electric field strength. With increasing electric field strength the nonaxisymmetric mode of instability is intensified. Moreover, as the electric field strength is increased, the breakup wavelength is decreased, which means the decrease in droplet size. Good agreements are obtained between the theoretical and experimental breakup wavelengths for the axisymmetric mode at low electric field strength. However, the breakup wavelengths for the nonaxisymmetric mode in practice are larger than those predicted by the theoretical analysis.
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  • Naoya Takahashi, Tsutomu Kambe, Tohru Nakano, Toshiyuki Gotoh, Kiyoshi ...
    Subject area: Kinetic and transport theory of fluids; physical properties of gases.
    1998 Volume 67 Issue 3 Pages 833-841
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    Two conditional averages for the increment Δ(x, x+r) ≡ T(x)-T(x+r) of the scalar field are estimated for DNS data:H(Δ)=‹&nabla_x2 Δ(x, x+r)|Δ(x, x+r)› andG(Δ)=‹|&nabla_x Δ(x, x+r)|2| Δ(x, x+r)›. The probability density function P(Δ) for Δ(x, x+r) isalso calculated.If Δ, P(Δ), H(Δ), and G(Δ) are expressedas θ, P(θ), h(θ), and g(θ) in a dimensionless form, the data analysis has revealed interesting simple relationships between them:(1) g(θ)P(θ) -- exp(-∫_0θ du h(u)/g(u)) derived by Ching and Kraichnan was numerically confirmed perfectly, (2) g(θ)P(θ) pass through an almost common point for any scale ranging from the dissipative to the inertial, to the energy containing scale, (3) by using fitting parameters A and β as a function of r, h(θ)/g(θ) is satisfactorily fitted by (A/β)tanh(βθ), and then g(θ)P(θ) -- (cosh β θ)^{-A/β^2}.These relations may be helpful to construct a turbulence model.
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  • Tsutomu Kawata, Jun–ichi Sakai, Jun Igarashi
    Subject area: Kinetic and transport theory of fluids; physical properties of gases.
    1998 Volume 67 Issue 3 Pages 842-849
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    We present results of magnetic flux-tube waves propagating along a current loop in a weakly ionized plasma, by means of a 3-D Neutral-MHD simulation code. After an impulsive velocity perturbation, the magnetic wave takes a tube structure and behaves as an isolated and stable string, to saya magnetic flux-tube soliton.Its velocity is associated with the electric current of the loop and a vortex induced inside the tube.There exists an interval of the electric current, where the velocity of the soliton is nearly proportional to the current.While on the stronger current region the velocity ofthe soliton is almost constant. The characteristics of the magnetic flux-tube solitonobserved in this simulation can be explained for a simple MHD model, in which we give necessary treatmentsto reduce the equation of current-vortex filament to a frame of integrable system.
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  • Hector Torres Silva, Paulo Hiroshi Sakanaka, Norma Reggiani
    Subject area: The physics of plasmas and electric discharges.
    1998 Volume 67 Issue 3 Pages 850-857
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    Electromagnetic waves in a magnetized chiral-plasma medium are studied. Using the Maxwell's equations and the proposed constitutive relations for a chiral-plasma medium, we derive the vectors E and H equations and from these equations, dispersion relations and E-field polarizations are founded. At high frequency, the obtained results for waves propagating parallely to the external magnetic field in a cold magnetized chiro-plasma are compared with typical results obtained for a cold plasma. For circularly polarized waves, a new mode conversion is founded due to the chiral effect. The chiral rotation is obtained and compared with the Faraday rotation. For waves propagating across the magnetic field, we found a shift of the cut-offs of ordinary and extraordinary waves, on the lower branch of the extraordinary wave mode there is no more bands of forbidden frequencies and the reflection point vanishes. At low frequency the effect of the chiral parameter on the fast and slow wave dispersion relations is moderate.
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  • Kanji Tsurugida, Ken Kouzuma, Masahisa Otsubo, Nobuaki Ikuta
    Subject area: The physics of plasmas and electric discharges.
    1998 Volume 67 Issue 3 Pages 858-862
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    A simple method for the measurement of electron drift velocity in gases under electric fields is presented.In this method, sinusoidally modulated electron current through the drift space is measured with a lock-in amplifier in place of using two shutters.The phase delay of the electron current referred to the electron release rate from the cathode gives an accurate mean transit time of electrons through the drift distance between the cathode and anode.The results of preliminary measurements of the electron drift velocity in argon are in good agreement with formerly reported data.In spite of simple procedures, this method will be useful for accurate measurements of electron drift velocity in various gases over wide ranges of the reduced electric field.
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  • Masayoshi Taguchi
    Subject area: The physics of plasmas and electric discharges.
    1998 Volume 67 Issue 3 Pages 863-869
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    The neoclassical transport theory in a presence of the temperature anisotropy in the equilibrium distribution function is developed in a large aspect-ratio tokamak. Using a model collision operator, the transport coefficients for the cross-field fluxes and the bootstrap current are explicitly calculated in the banana regime. The electron perpendicular (parallel) heating is found to increase (decrease) the cross-field particle and energy fluxes of electrons and the bootstrap current. The cross-field energy flux of ions are increased (decreased) by the perpendicular (parallel) ion heating. The cross-field fluxes and the bootstrap current are also shown to have the component proportional to the radial electric field.
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  • Wakako Shiratori, Jun–ichi Sakai, Mitsuhiro Nambu
    Subject area: The physics of plasmas and electric discharges.
    1998 Volume 67 Issue 3 Pages 870-875
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    The dynamics of the electron-ion plasma cloud moving perpendicular to an ambient magnetic field in the background plasma is investigated by means of a three-dimensional, electromagnetic, and relativistic particle simulation code. The simulation results show that the cloudseparates into electrons and ions due to their gyromotions withLarmor radius of V0cj (V0 is the initialcloud velocity and ωcj is the cyclotron frequency of species j). Consequently, electromagnetic and whistler waves are excited from the cloud due to coherent gyration of cloud electrons.In addition, Langmuir waves are also excited along a magnetic field.It is shown that cloud electrons are accelerated by Langmuir wavesalong the magnetic fieldand the population inversion is created in the velocitydistribution of cloud electrons. The accelerationmechanism of cloud electrons is due to Landau resonance between Langmuir waves and cloud electrons. We apply our results to theelectron acceleration mechanism from plasma cloud produced near a comet nucleus, which may explain recent observation of X-ray from comet Hyakutake.
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  • Ryoichi Minai, Isao Katanuma, Teruo Tamano, Kiyoshi Yatsu
    Subject area: The physics of plasmas and electric discharges.
    1998 Volume 67 Issue 3 Pages 876-881
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    We investigate the ion axial confinement time and the ion endloss spectrum in a wide range of collision frequency in GAMMA10 tandem mirror by using Monte-Carlo simulation. It is found that in the two limits of collision frequency, the confinement time is smaller than the theoretical value on square well model. Also, unlike the square well model, the ion endloss spectrum consists of two elements where collision frequency is very small.
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  • Kenjiro Sugio, Yoshiharu Shimomura, Tomas D. de la Rubia
    Subject area: Structure of liquids and solids; crystallography.
    1998 Volume 67 Issue 3 Pages 882-889
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    A computer simulation of molecular dynamics is carried out to study theeffects of a sigma 5 twist boundary on the formation of displacement damagecascades in silver.When a displacement damage cascade forms near the boundary, interstitial atoms are attracted and segregate on the boundary.The number of Frenkel defects after the formation of damage cascadenear the boundary is more than that in a perfect crystal.The segregation of interstitial atoms is due to the interaction withthe boundary through the strain field.The movement of interstitial clusters in a strain field is due toa ‹ 110› crowdion migration.The larger interstitial clusters are attracted to the boundaryat the larger separation.When a damage cascade forms on the boundary, the crystal structureof sigma 5 boundary is modified during the solidification of its molten core.The segregation of interstitial atoms on stacking fault and twin boundaryon the formation of damage cascade was also studied.The segregation of interstitial to these defect planes during the formationof damage cascade was not observed.The preferential segregation of interstitial and vacancy on these planesis due to a strong trapping of point defects on these planes.
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  • Yosuke Yoshimura
    Subject area: Structure of liquids and solids; crystallography.
    1998 Volume 67 Issue 3 Pages 890-898
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    Non-linear behavior of the chemical potential of a two-dimensional infinitely-thin hard needle with respect to the needle length in a hard disk fluid is studied. The expansion of the chemical potential with respect to the needle length shows that the mean force acting on the needle along the needle axis, i.e. the needle length derivative of the chemical potential with the reverse sign, is dependent on the needle length. Damped oscillatory behavior of the mean force was found by a Monte Carlo calculation with the insertion-and-elongation procedure. The pair distribution function between the needle and the hard disk changed drastically with the needle length.
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  • Takeshi Nishikawa, Kohei Yokoi
    Subject area: Lattice dynamics and crystal statistics.
    1998 Volume 67 Issue 3 Pages 899-902
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    Crystal structures of C76 with (D_2) symmetry were calculated by molecular dynamics simulation using reliable potential function. We observed three phases in the crystal structure, a face center cubic (fcc) and two hexagonal (hex1, and hex2).The lattice constants and transition temperatures of fcc and hex2 were good in agreement with experiments.The lattice constants of the crystals were a = 15.50 Å for the fcc and a = 10.93, c = 17.50 Å for the hex2, respectively, at room temperature. The transition temperatures were about 200 K for the fcc, and about 350 and 500 K for the hex2. However any phase corresponding to the hex1 has not been reported in experiments.The lattice constants were a = 10.50, c = 18.42 Å at room temperature and transition temperatures were about 100 and 400 K.The calculated lattice stabilizing energy and density of hex1 were greater than those of hex2.
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  • Dal–Young Kim, Jong–Gul Yoon, Sook–Il Kwun
    Subject area: Equations of state, phase equilibria, and phase transitions.
    1998 Volume 67 Issue 3 Pages 903-906
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    Linear birefringence behavior of Rb2ZnCl4, K2ZnCl4, and [N(CH3)4]2ZnCl4 were studied in the critical region of the normal-incommensurate phase transition. Exisence of linear birefringence tail above the transition temperature was observed. It wasascribed to the fluctuation effect on the linearbirefringence. Results of scaling analysis imply that the exponent of LB behavior is not 1- αbut 2β, contrary to the previous LB study.Contribution of the fluctuation to linear birefringence behavior isdiscussed comparing to XRD experiments.
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  • Kêiichiro Aizu
    Subject area: Equations of state, phase equilibria, and phase transitions.
    1998 Volume 67 Issue 3 Pages 907-911
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    This paper is concerned with a transition from an artificially incommensurately undulated prototypic phase to a ferroic phase, and also with U-ferroelectricity (which means ferroelectricity that should vanish if the prototypic phase is brought from undulated to homogeneous). Prototype undulation can be represented by the undulation of a set of declension parameters (denoted by δ, ε, …). All previous papers that dealt with prototype undulation assumed only one declension parameter. In contrast the present paper assumes two. One case is studied, whose definition includes assuming δ =Uδ, cos, (ĥx+\hat{θ}δ) and ε =Uε, cos, (ĥx+\hat{θ}ε) with all high harmonics ignored. The expressions of spontaneous polarization and dielectric susceptibility are deduced, the former of which indicates that, if and only if Uδ≠ 0, Uε≠ 0 and sin, (\hat{θ}δ-\hat{θ}ε)≠ 0, the ferroic phase is ferroelectric.
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  • Jirka Hlinka, Yoshihiro Ishibashi
    Subject area: Equations of state, phase equilibria, and phase transitions.
    1998 Volume 67 Issue 3 Pages 912-915
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    Relative heights of the steps in the temperature dependence of thermal strain along the direction of modulation, corresponding to the phase transitions between various commensurate phases in betaine calcium chloride dihydrate (BCCD), are interpreted within a simple discrete model.
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  • Yasuhiro Senda, Fuyuki Shimojo, Kozo Hoshino
    Subject area: Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties).
    1998 Volume 67 Issue 3 Pages 916-921
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    The ionic configuration and the electronic properties of the ground states of NaN and LiNaN-1 (N≤8) clusters are investigated by an ab initio pseudopotential calculation, in which the electronic states are calculated by the density functional theory in the local spin-density approximation using the norm-conserving pseudopotentials and the total energy is minimized by the conjugate gradient method. It is shown that the Li atom is located near the center of LiNaN-1 clusters and that this feature can be explained based on the difference in the employed pseudopotentials for Li and Na ions and on the electronic density distributions of the clusters.The observed Li enrichment in the mass spectra and its size dependencecan also be explained.
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  • Hisashi Shimizu, Masafumi Shirai, Naoshi Suzuki
    Subject area: Electron states in condensed matter.
    1998 Volume 67 Issue 3 Pages 922-926
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    The electronic and magnetic properties of NaCl-type FeN and thehyperfine field at Fe sites in NaCl-type FeN are investigated by bandcalculations using a full-potential linearized augmented-plane-wave method. The equilibrium lattice constant obtained theoretically (--4.0 Å)is much smaller than the experimental value (4.50 Å). For our estimated equilibrium lattice constant the ferromagnetic stateis more stable than the non-magnetic state and two kinds of antiferromagneticstate (q=(π, π, π), q=(0, 0, π)). The hyperfine field of the ferromagnetic state is very smallat the lattice constant a=4.0 Å, and it decreases withincreasing the lattice constant. The hyperfine field of the q=(π, π, π) antiferromagnetic stateis also rather small at a=4.0 Å, but its magnitudeincreases considerably with increasing a and at a=4.5 Å it becomescomparable with the hyperfine field of bcc Fe. Furthermore, at a=4.5 Å the q=(π, π, π) antiferromagneticstate is more stable than the ferromagnetic state.
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  • Akito Kobayashi, Tamifusa Matsuura
    Subject area: Electron states in condensed matter.
    1998 Volume 67 Issue 3 Pages 927-940
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    We investigate the antiferromagnetic moment of heavy quasi-particles in the U-infinite degenerate Anderson lattice model of the square lattice where the renormalized bands have the nested Fermi surface.The conduction electron component Mc and the f-electron component Mf of the antiferromagnetic moment are treated separately.We find that Mf /Mc is ruled by the single parameter m* /m as Mf /Mc ≅ (gf /gc)(m* /m).In addition, in the Kondo regime, Mf is almost proportional to the number of f-electrons nf, and independent of m* /m, while Mc is almost proportional to (m* /m)-1, i.e. Mf ≅ gf μB · k nf and Mc ≅ gc μB · k ρc TK, where ρc represents the D.O.S of the conduction electron band.The coefficient k depends on local moments Mion of f-electrons under crystal fields and the degree of the nesting effect.At the limiting case that the Fermi surface is perfectly nested and Mion=\frac{5}{2}gf μB, k reaches about 1, thus Mf reaches about 1gf μB at the limit of nf → 1, i.e. 40% of Mion, where the total moment M (=Mc + Mf)nearly equals Mf in the Kondo regine. As the degree of the nesting effect decreases, k approaches zero, and then the system becomes nonmagnetic when k equals zero.
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  • Ryousuke Shiina, Osamu Sakai, Hiroyuki Shiba, Peter Thalmeier
    Subject area: Electron states in condensed matter.
    1998 Volume 67 Issue 3 Pages 941-949
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    We propose a theory of CeB_6 in a magnetic field by extending and slightly modifying a previous paper.The antiferro-quadrupolar ordering induces dipoles and octupoles when the magnetic field is applied. The nature of those field-induced multipoles is studied by changing the direction of the field. It is shown that the contradiction between NMR and neutron diffraction is resolved by taking into account the influence of octupoles. Thus it is concluded that CeB_6 is the first example in which the octupoles play a crucial role on the anomalous f-electron ordered phase.
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  • Hikaru Kitamura, Setsuo Ichimaru
    Subject area: Electron states in condensed matter.
    1998 Volume 67 Issue 3 Pages 950-963
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    First-principles formulations of the equations of state for hydrogenin metallic and insulator phases are presented, leading to a phasediagram predicting first-order metal-insulator transitions in dense hydrogen. The theory explicitly takes into account the effects ofstrong electron-ion coupling near the transitions as well as those oflowering or elimination of the atomic and/or molecular levels due toplasma screening. It is shown that the results of recentshock-compression experiments prove consistent withsuch first-order insulator-to-metal transitions. These observations predict a discontinuous distribution of density and resistivity with alarge magnetic Reynolds number near the Jovian surface; the latentheat through the metal-to-insulator transitions is estimated.
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  • Yasumasa Hasegawa, Keita Kishigi, Mitake Miyazaki
    Subject area: Electron states in condensed matter.
    1998 Volume 67 Issue 3 Pages 964-970
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    We study the Field-Induced Spin Density Wave in the presence of theperiodic potential which is treated non-perturbatively.We obtain that both even and odd subphases weakly depend on the magneticfield in the strong potential case, while in the perturbation only even subphases strongly dependon the magnetic field. We discuss the recently reported phase diagram in (TMTSF)_2ClO_4.
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  • Jian Dong, Kyuya Yakushi, Kazuo Takimiya, Tetsuo Otsubo
    Subject area: Electron states in condensed matter.
    1998 Volume 67 Issue 3 Pages 971-977
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    Pseudo-one-dimensional charge-transfer salt DMTSA-BF4 shows high electrical conductivity (σ RT≈ 500, Scm-1) and metallic temperature dependence down to ca. 160, K, in contrast to the conventional half-filled organic conductors which are regarded as Mott insulators. The pseudo-one-dimensionality is evidenced by the polarized reflectance spectra. The electrical resistivity, thermopower, magnetic susceptibility, and polarized reflectance spectrum suggest that DMTSA-BF4 is a metal above ca. 150, K. This compound is the first metal among the 1:1 organic charge-transfer salts. The low-temperature reflectance spectrum suggests that the glide plane symmetry is broken below 150, K and the fluctuation of this broken symmetry is already observed at room temperature. The metal-insulator transition around 150, K is regarded as Peierls transition. The Hubbard parameter U/W is estimated to be <0.8, which may be the possible reason for the metallic nature in high-temperature phase.
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  • Ichiro Ohsaki, Tamio Oguchi
    Subject area: Electronic structure and electrical properties of surfaces, interfaces and thin films.
    1998 Volume 67 Issue 3 Pages 978-982
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    The stability of Cu(001)-(2×1)-Li and Al(001)-c(2×2)-Nasystems, in which the adatoms (Li or Na) occupy substitutional sites are investigated based on first-principles electronic structure calculations.The total energies of the systems are calculated and compared, by considering some related surface structures and optimizing the structuralparameters involved.The stability is discussed in terms of vacancy-formation and binding energies. Change in work function by adsorption is also discussed.
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  • Hideharu Ishida, Ryusuke Ikeda
    Subject area: Superconductivity.
    1998 Volume 67 Issue 3 Pages 983-995
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    Effects of a repulsive interaction between electrons in two dimensional (2D)disordered superconductors are examined by neglecting the localization effect on noninteracting electrons and through a derivation of quantum Ginzburg-Landau (GL) action in a high magnetic field and at low temperatures. By examining the nature of perturbation series in the repulsive interaction, we find a strong evidence enough to believe that the mean field GL equation is well-defined even at zero temperature (T=0). The resulting functional form of the dissipative term suggests a possibility that the dissipative time scale associated with the diagonal fluctuation conductivity may reduce to zero in the limit of T=0, leading to a significant growth of purely dissipative quantum fluctuation at a finite magnetic field in T=0 limit. On the other hand, we find that the effective strength of electron-hole assymmetry of the fluctuation, associated with the Hall fluctuation conductivity, also decreases due to the electron repulsion but cannot vanish in general at T=0. It is pointed out on the basis of the present calculation that, in general, the Hc2(T)-line in T=0 limit should be closely related to a reduction of the dissipative dynamics on cooling.
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  • Tatsuo C. Kobayashi, Tadashi Miyazu, Nao Takeshita, Katsuya Shimizu, K ...
    Subject area: Superconductivity.
    1998 Volume 67 Issue 3 Pages 996-999
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    Enhancement of superconducting transition temperature Tc is confirmed at around 16 GPa in the pressure-induced superconductor CeCu_2Ge_2.The superconducting Hc-Tc phase diagrams at the low-Tc and high-Tc pressure regions indicates that the heavy quasi particles form the singlet Cooper pairs.At both low-Tc and high-Tc pressure regions, Fermi liquid behavior of ρ-- AT^2 is observed only at low temperatures below 1 K in the normal state induced by the external field above Hc2.At 21 GPa where the superconductivity disappears down to 50 mK, the temperature region following ρ-- AT^2 increases drastically up to 40 K and the coefficient A decreases rapidly.These results indicate that the strongly correlated electrons are responsible essentially for the appearance of superconductivity in this system.
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  • Takashi Tonegawa, Toshiya Hikihara, Makoto Kaburagi, Tomotoshi Nishino ...
    Subject area: Magnetic properties and materials.
    1998 Volume 67 Issue 3 Pages 1000-1013
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    We investigate both analytically and numerically the ground-state andthermodynamic properties of the quantum mixed spin-1/2-1/2-1-1chain described by the Hamiltonian \hbox{{\cal H}=∑_{l=1}N/4\bigl(J_1, {\vec s}_{4l-3}·{\vec s}_{4l-2}+J_2, {\vec s}_{4l-2}· {\vec S}_{4l-1}+J_3, {\vec S}_{4l-1}· {\vec S}_{4l}+J_2, {\vec S}_{4l}·{\vec s}_{4l+1}\bigr)}, where two \hbox{S=1/2} spins({\vec s}_{4l-3} and {\vec s}_{4l-2}) and two \hbox{S=1} spins( {\vec S}_{4l-1} and {\vec S}_{4l}) are arranged alternatively. Inseveral limiting cases of J_1, J_2, and J_3 we apply the Wigner-Eckarttheorem and carry out a perturbation calculation to examine the behavior ofthe massless lines where the energy gap vanishes. Performing a quantum MonteCarlo calculation without global flips at a sufficiently low temperature forthe case where J_1=J_3=1.0 and J_2>0, we find that theground state of the present system in this case undergoes a second-order phasetransition accompanying the vanishing of the energy gap at\hbox{J_2=J2c with J2c=0.77±0.01}. We alsofind that the ground states for both \hbox{J_22c} and\hbox{J_2>J2c} can be understood by means of thevalence-bond-solid picture. A quantum Monte Carlo calculation which takes theglobal flips along the Trotter direction into account is carried out toelucidate the temperature dependences of the specific heat and the magneticsusceptibility. In particular, it is found that the susceptibility per unitcell for J_2=0.77 with J_1=J_3=1.0 takes a finite value atabsolute zero temperature and that the specific heat per unit cell versustemperature curve for J_2=5.0 with J_1=J_3=1.0 has a doublepeak.
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  • Masafumi Takagaki, Takuya Kawakami, Norikazu Tanaka, Masafumi Shirai, ...
    Subject area: Magnetic properties and materials.
    1998 Volume 67 Issue 3 Pages 1014-1016
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    Pressure influence on the electronic band structure of NiAs-type CrTe is studied for non-magnetic, ferromagnetic and antiferromagnetic states by using a self-consistent LAPW method. The total energy is calculated as a function of the lattice spacing a, keeping the ratio c/a as the observed value. The ferromagnetic state is stable energetically among three states for a>3.83, A. For a<3.83, A, the energy of antiferromagnetic state becomes lower than that of ferromagnetic state. Therefore pressure-induced ferromagnetic→ antiferromagnetic transition is expected at about 20, GP. For the ferromagnetic state, which is realized below TC=340, K, the theoretical lattice spacing a is obtained as 4.180, A, which agrees fairly well with the observed one (aobs=3.981). The magnetic moment arises from mainly Cr-site and it is remarkably reduced by the pressure as observed. A small magnetic moment is induced at Te-site in the direction antiparallel to the moment at Cr-site.
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  • Tetsuo Honma, Hiroshi Amitsuka, Shinji Yasunami, Kenichi Tenya, Toshir ...
    Subject area: Magnetic properties and materials.
    1998 Volume 67 Issue 3 Pages 1017-1028
    Published: March 01, 1998
    Released on J-STAGE: October 01, 1999
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    The magnetic, transport, and thermal properties have been studied in UPd2Si2 single crystals by various experiments including neutron diffraction and ultra-high-field (H < 1 MOe) magnetization. The entire feature of H--T magnetic phase diagram has been obtained, for the first time. Three distinct ordered phases are observed, with a strong uniaxial anisotropy along the tetragonal c-axis. One of the notable features revealed in the ordered phases is a formation of an incommensurate-longitudinal-sine-wave (ICLSW) modulation in the temperature range 108 K < T < 135 K, where the propagation vector Q (--0.71c* at 135 K) varies continuously as a function of temperature, with no admixture of harmonics. The magnetic susceptibility exhibits an unusual ferromagnetic enhancement in this antiferromagnetically ordered state. The entropy analyses using a non-5f analog ThPd2Si2 have confirmed that the anomalous magnetic properties of UPd2Si2 are ascribed to the 5f moments of uranium ions, which are replaceable with Ising pseudo-spins. A phenomenological argument has been demonstrated on the basis of the axial-next-nearest-neighbor Ising (ANNNI) model within a mean-field approximation. The calculations with a finite-size approximation reproduce the observed magnetic phase diagram surprisingly well.
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