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Sergei Yu. Sakovich
Subject area: Mathematical methods in physics.
1997 Volume 66 Issue 9 Pages
2527-2529
Published: September 01, 1997
Released on J-STAGE: October 01, 1999
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The Painlevé test for integrability is applied to the Kodama-Hasegawa higher-order nonlinear Schrödinger equation which describes ultra-short light pulses in optical fibers. Only the four known integrable cases of this equation pass the test if the standard Painlevé property is required. However, there is another case of this equation with the weak Painlevé property and softer constraints on parameters. The integrability of this new case remains unkhown, and its possible kind is discussed.
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Ryogo Hirota
Subject area: Mathematical methods in physics.
1997 Volume 66 Issue 9 Pages
2530-2532
Published: September 01, 1997
Released on J-STAGE: October 01, 1999
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“Molecule solutions” of a system of coupled nonlinear differential-difference equations \frac{∂ v_n
(i)}{∂ t}-[∑
N_{j, k=1} c
j, kv_n
(j)v_n
(k)][v
n+1(i)-v
n-1(i)]=0, \quad i=1, 2, …, N where the coefficients c
j, k are arbitrary constants, are expressed by pfaffians. We mean by “molecule solutions” that all v_n
(i) for i=1, 2, …, N, satisfy the boundary conditions: v_n
(i)=0 at n=0.
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Takashi Matsuyama, Katsuya Honda
Subject area: Statistical physics and thermodynamics.
1997 Volume 66 Issue 9 Pages
2533-2536
Published: September 01, 1997
Released on J-STAGE: October 01, 1999
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We report computer simulation results ofthe restricted solid-on-solid model as a prototypeof rough surface growth on various fractal substrates with fractal dimensions 1 < d_f < 2.The surface width was examined to show a power law behavior such as t
β with time t.We find different values of β for two substrates with the same d_f, whichindicates explicitly that the universality classis not determined by only the substrate dimension d_f.Some resulting values of β fit fairly well with the Kim-Kosterlitz (KK)conjecture, β = 1/(d_f+2), while others do not agree with it. Using the effective dimension d derivedthrough the averaged neighboring cell number, we also investigate the d dependence of β values, so that the latter class is found to approach the KK curve, although the former is distant from it.
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Yoon–Pyo Lee, Sarng Woo Karng, Jin–Seok Jeon, Ho–You ...
Subject area: Fluid dynamics.
1997 Volume 66 Issue 9 Pages
2537-2540
Published: September 01, 1997
Released on J-STAGE: October 01, 1999
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The shock pulse emanating from a sonoluminescing gas bubble was calculated by using the analytical solutions of the conservation equations for the gas inside the bubble and the Kirkwood-Bethe hypothesis for the outgoing wave. The rise time and the magnitude of the pulse signal are in good agreement with the observed values, which may provide the approximate value of the gas pressure at near the collapse of the sonoluminescing gas bubble.
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Levan N. Tsintsadze, Nodar L. Tsintsadze, Kyoji Nishikawa
Subject area: Kinetic and transport theory of fluids; physical properties of gases.
1997 Volume 66 Issue 9 Pages
2541-2544
Published: September 01, 1997
Released on J-STAGE: October 01, 1999
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The effects of black-body radiation emitted from a high temperature radiation source on electrostatic plasma wave characteristics in a relatively cold tenuous plasma are theoretically investigated. The ponderomotive force of the photons perturbed by the electron density fluctuation is taken into account.It is shown that the effect is in general very small, but has a logarithmicsingularity which corresponds to a radiation induced zero-sound. A significanteffect can be expected in a narrow frequency range in which the zero-soundcouples with the electron plasma wave.
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Ryoichi Yamamoto, Akira Onuki
Subject area: Structure of liquids and solids; crystallography.
1997 Volume 66 Issue 9 Pages
2545-2548
Published: September 01, 1997
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We study a highly supercooled two-dimensional fluid mixture via molecular dynamics simulation. We follow bond breakage events among particle pairs, which occur on the scale of the α relaxation time τ
α. Large scale heterogeneities analogous to the critical fluctuations in Ising systems are found in the spatial distribution of bonds which are broken in a time interval with a width of order 0.05τ
α. The structure factor of the broken bond density is well approximated by the Ornstein-Zernike form.The correlation length is of order 100 σ
1 at the lowest temperature studied, σ
1 being the particle size.The weakly bonded regions thus identified evolve in time with strong spatial correlations.
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Setsuo Misawa
Subject area: Quantum fuids and solids: liquid and solid helium.
1997 Volume 66 Issue 9 Pages
2549-2551
Published: September 01, 1997
Released on J-STAGE: October 01, 1999
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The Fermi liquid model predicts that the magnetic susceptibility of a Fermi liquid should universally exhibit a maximum as a function of temperature. This universality has been confirmed through observations in itinerant electron systems in 3d, 4d and 5d metals. Here we argue that the maximum should be observed in liquid
3He. We estimate the temperature of the maximum and the peak height of the susceptibility for liquid
3He from theory and experiment. We predict that the susceptibility increases by 0.24\ emperature range of 0 mK to 40 mK, at which the susceptibility nearly becomes maximum.The possibility of detecting this maximum is discussed.
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Tatsuya Fujii, Yasumasa Tsukamoto, Norio Kawakami
Subject area: Electron states in condensed matter.
1997 Volume 66 Issue 9 Pages
2552-2555
Published: September 01, 1997
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We exactly calculate the momentum-dependent critical exponents for spectral functions in the one-dimensional anisotropic t-J models with a gap either in the spin or charge excitation spectrum. Our approach is based on the Bethe ansatz technique combined with finite-size scaling techniques in conformal field theory. It is found that the spectral functions show a power-law singularity, which occurs at frequencies determined by the dispersion of a massive spin (or charge) excitation.We discuss how the nontrivial contribution of a massive excitation controls the singular behavior in optical response functions.
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Seiji Higashitani
Subject area: Superconductivity.
1997 Volume 66 Issue 9 Pages
2556-2559
Published: September 01, 1997
Released on J-STAGE: October 01, 1999
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A possible mechanism of paramagnetic Meissner effect observed in some high-temperature superconductors is proposed. It is shown that a paramagnetic Meissner current flows if there exists a large quasi-particle density of states around zero energy in the energy gap. This suggests that the paramagnetic Meissner effect is associated with a zero-bias conductance peak which has often been observed in the tunneling experiments of high-temperature superconductors. The paramagnetic effect caused by the zero-energy excitations is consistent with the experiments.
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Naoto Metoki, Yoshinori Haga, Yoshihiro Koike, Naofumi Aso, Yoshichika ...
Subject area: Superconductivity.
1997 Volume 66 Issue 9 Pages
2560-2563
Published: September 01, 1997
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Neutron scattering experiments have been carriedout in order to study the interplay betweenmagnetism and superconductivity in a heavy fermionsuperconductor, UPd_2Al_3. We have observed1∫ensity below the superconducting transitiontemperature T
c. This is direct evidence forthe coupling of the magnetic order parameter withthe superconducting one. Furthermore, we haveobserved a spin excitation gap associated withsuperconductivity. The gap energy Δ E
g increases continuously from Δ E
g =0 to 0.4 meV with decreasing temperaturefrom T
c to 0.4 K. This gap energycorresponds to 2k
BT
c, which issmaller than the superconducting gap expected fromthe BCS theory (3.5k
BT
c). Theseresults are indicative of the strong interplaybetween magnetism and superconductivity.
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Shoji Kometani, Mikhail I. Eremets, Katsuya Shimizu, Michihiro Kobayas ...
Subject area: Superconductivity.
1997 Volume 66 Issue 9 Pages
2564-2565
Published: September 01, 1997
Released on J-STAGE: October 01, 1999
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The electrical resistance of sulfur has been measured under pressures up to 100, GPa and temperatures down to 70, mK. Under pressures approaching 100, GPa, sulfur shows metallic reflection comparable to that of used Pt electrodes. The temperature dependence of the resistance reveals metallic behavior, and the sharp drop of the resistance at around 15, K and 100, GPa is due to superconducting transition as the transition temperature shows typical magnetic field dependence.
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Hiroyuki Suzuki, Mitsuo Kasaya, Takashi Miyazaki, Yuichi Nemoto, Terut ...
Subject area: Magnetic properties and materials.
1997 Volume 66 Issue 9 Pages
2566-2568
Published: September 01, 1997
Released on J-STAGE: October 01, 1999
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PrPtBi is found to crystallize in the cubic MgAgAs-type structure. At the specific heat, an anomaly appears at about 1.35 K, the temperature at which the entropy approaches the value --Rln2. Data on the specific heat and magnetic susceptibility suggest that the crystalline-electric-field (C.E.F) ground state of PrPtBi is the non-Kramer's doublet Γ_3. Below about 2.5 K, we observe a huge softening of the elastic constant C_T, which suggests the onset of electric quadrupolar ordering. The Hall constant gives evidence that PrPtBi is a low-carrier system, as suggested from band calculations.
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Shunsuke Yoshii, Hiroyuki Suzuki, Daisuke Tazawa, Mitsuo Kasaya
Subject area: Magnetic properties and materials.
1997 Volume 66 Issue 9 Pages
2569-2571
Published: September 01, 1997
Released on J-STAGE: October 01, 1999
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We have synthesized CePtAs single crystals for the first time and found that they crystallize with a hexagonal GaGeLi-type crystal structure. Magnetic and specific heat measurements on single crystals indicate that CePtAs is an antiferromagnet with a Néel temperature of 1 K. The magnetization curve at 0.54 K revealed that CePtAs exhibits a metamagnetic transition along both the a- and c-axes. Transport properties indicate a strong anisotropy. The electrical resistivity along the c-axis is Kondo-like, while it is metallic within the c-plane. The Hall constant is negative for the magnetic field within the c-plane, whereas it is positive for the magnetic field along the c-axis. These results along with the results on LaPtAs suggest that CePtAs is a rare strongly-correlated electron system accompanied with an anisotropic Kondo effect and metamagnetic transition.
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Satoru Noguchi, Kiichi Okuda, Tomohiro Adachi, Yoshinori Haga, Etsuji ...
Subject area: Magnetic properties and materials.
1997 Volume 66 Issue 9 Pages
2572-2575
Published: September 01, 1997
Released on J-STAGE: October 01, 1999
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A single crystal of a new ternary silicide U
1.2Fe
4Si
9.7 has been synthesized by the Czochralski method and characterized by X-ray diffraction, magnetization, specific heat and electrical resistivity measurements. It crystallizes in the hexagonal Er
1.2Fe
4Si
9.8-type structure characterized by a disordered two-dimensional layer of U-atoms. The lattice parameters are a = 3.956(1) Å and c = 15.055(2) Å. Magnetic susceptibility follows the Curie-Weiss law down to 40 K with the effective magnetic moment of 2.4 μ
B/U. The electronic specific heat coefficient, γ of 180 mJ/K
2mol·U was obtained. A large residual resistivity due to the disordered structure of the U-Si layer was observed.
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Takashi Ono, Takeshi Nishimura, Manabu Katsumura, Tetsuya Morita, Mits ...
Subject area: Magnetic properties and materials.
1997 Volume 66 Issue 9 Pages
2576-2579
Published: September 01, 1997
Released on J-STAGE: October 01, 1999
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Ground-state properties of ferrimagnetic XXZ chains with alternating spins S
A and S
B with nearest-neighbor exchange interaction are discussed based upon the results for finite-size systems obtained mainly by the exact diagonalization method and partly by the density matrix renormalization group method. For -1<Δ<1, where Δ is the parameter of anisotropy of the interactions, the ground state is unique or doubly degenerate and gapless. When Δ=1, the ground state of 2N sites is the state with total spin N|S
A-S
B|, and has nonvanishing Néel long-range order parameter. For Δ>1, the ground state is doubly degenerate Néel long-range ordered state with a finite energy gap.
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Tomohiko Miyazaki, Matthias Troyer, Masao Ogata, Kazuo Ueda, Daijiro Y ...
Subject area: Magnetic properties and materials.
1997 Volume 66 Issue 9 Pages
2580-2583
Published: September 01, 1997
Released on J-STAGE: October 01, 1999
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The effects of non-magnetic impurities randomly doped into a two-leg Heisenberg spin ladder are investigated. Using the continuous time quantum Monte Carlo loop algorithm we calculate the uniform and staggered susceptibilities of such a system. The obtained uniform susceptibility is well described in terms of an effective model of weakly interacting local moments induced by non-magnetic impurities for a 1 staggered susceptibility however is significantly enhanced over that in the effective model already at 1 Using a mean field approximation for the interladder coupling, we explain qualitatively the phase diagram of Sr(Cu
1-xZn
x)
2O
3.
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Yumino Hayase
Subject area: Other areas of research of general interest to physicists.
1997 Volume 66 Issue 9 Pages
2584-2587
Published: September 01, 1997
Released on J-STAGE: October 01, 1999
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We study numerically, the collision and self-replication of pulses in a reaction-diffusion system of the activator-inhibitor type.We established the following new properties of pulse dynamics.Two propagating pulses result in a localized oscillatory domainafter a head-on collision.However this domain is a transient one and disappears after one period leaving new pulses propagating outward.In another parameter regime, a traveling pulsebreaks into a pair of pulses propagating in opposite directions.
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Nobumasa Sugimoto, Kazufumi Ikeda
Subject area: Mathematical methods in physics.
1997 Volume 66 Issue 9 Pages
2589-2600
Published: September 01, 1997
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This paper presents a new integral-equation method to solve Burgers equation for nonlinear acoustic waves in a duct spreading geometrically along its axis. The nonlinear integral equation is derived by effecting the Cole-Hopf transformation to the Burgers equation and then by applying the Green's function to the equation thus transformed. Under a step initial condition, two methods are demonstrated to solve the integral equation, one being the method of perturbation expansion and the other the method of successive approximation. They are exemplified by solving evolution of an acoustic shock wave in a duct whose cross-sectional area changes abruptly in the form of a step function. It turns out that the method of perturbation expansion gives rise to the non-uniformity to fail in describing a long-time and far-field behavior. By contrast, the method of successive approximation solves the linearized integral equations by iterations infinite times to derive exact solutions if the convergence is attained. It is revealed that the method of successive approximation can yield a uniformly valid solution. Finally there are given some discussions on the properties of the nonlinear integral equation and on a trial approach to exact solutions by the method of successive approximation.
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Jorge Fujioka, Aurea Espinosa
Subject area: Mathematical methods in physics.
1997 Volume 66 Issue 9 Pages
2601-2607
Published: September 01, 1997
Released on J-STAGE: October 01, 1999
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An extended nonlinear Schrödinger equation, with positive fourth-order dispersion and a quintic nonlinearity, is shown to possess a soliton-like solution which exists in resonance with linear dispersive waves, but emits no radiation at all. When this solution is perturbed the emission of radiation begins. An approximate variational analysis and direct numerical integrations are carried out to show that this soliton-like solution is robust enough to resist small perturbations without being dispersed away. Initial conditions which are close to the exact solution evolve into quasi-stationary solutions which emit radiation, but maintain their shapes over extremely long distances.
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Takayuki Tsuchida, Yasumasa Kajinaga, Miki Wadati
Subject area: Mathematical methods in physics.
1997 Volume 66 Issue 9 Pages
2608-2617
Published: September 01, 1997
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Multi-Hamiltonian structure of the Lotka-Volterra model (for short, Volterra model) with an even period is studied. This model is known to have bi-Hamiltonian structure. In connection with the canonical formulation of the Toda lattice, we introduce a new (third) set of Poisson bracket and Hamiltonian for this model. Referring the well-known complete integrability of the Toda lattice, we prove the complete integrability of the Volterra model for the Poisson bracket which we define.
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Tomohiro Sasamoto, Miki Wadati
Subject area: Mathematical methods in physics.
1997 Volume 66 Issue 9 Pages
2618-2627
Published: September 01, 1997
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Proposed is a method to construct a stationary state of one-dimensional integrable systems in the form of products of matrices. This is a generalization of the so-called “matrix product ansatz (MPA)”. The key idea is that the matrices are chosen to constitute the Zamolodchikov-Faddeev algebra (ZF-algebra) for the R-matrix and the K-matrix, which are the solutions of the Yang-Baxter equation (YBE) and the reflection equation (RE). It is shown that a matrix product state gives a simultaneous stationary state of commuting operators which are expressed in terms of the R-matrices and the K-matrices. As an example, a solution for the isotropic Heisenberg spin chain with non-diagonal boundary fields is given. The connection to the conventional MPA is clarified. Applications to other models and the relationship to the algebraic Bethe ansatz (ABA) are also discussed.
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Yoshihiro Yamazaki
Subject area: Statistical physics and thermodynamics.
1997 Volume 66 Issue 9 Pages
2628-2637
Published: September 01, 1997
Released on J-STAGE: October 01, 1999
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Elastic effects by cubic-tetragonal symmetry breaking on the ordering kinetics are investigated. We propose a coarse-grained model characterized by a Ginzburg-Landau free energy with nonconserved order parameters coupled to an elastic field. By numerical study we obtain an oval shaped domain and a square domain in two dimensions and a plate-like domain and a rod-like domain in three dimensions. And in the coarsening process, a striped pattern is obtained. These patterns are remarkably similar to morphologies observed in real cubic-tetragonal order-disorder alloys. Moreover, we study the dynamics during the coarsening process by analyzing the change of the total domain boundaries L
DB(t). L
DB(t) decreases as a power of time: t
-α (α>0). The exponent α becomes small with increasing the magnitude of the elastic effects.
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Yoshihiko Nonomura
Subject area: Statistical physics and thermodynamics.
1997 Volume 66 Issue 9 Pages
2638-2646
Published: September 01, 1997
Released on J-STAGE: October 01, 1999
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Ground-state properties of the two-dimensional S=1/2 Heisenberg Mattis model is investigated using the world-line quantum Monte Carlo method. Calculations of the spin glass order parameter show that the term proportional to L
-2 is dominant in the scaling of this order parameter, and that this order parameter increases monotonously as the concentration of ferromagnetic bonds, p, is enhanced. Simulations of the Néel order parameter and the staggered susceptibility show that the Néel-Mattis spin glass phase boundary of the present model is consistent with the critical concentration of the two-dimensional Ising Mattis model, p
c~= 0.147, and that the critical exponents of these quantities are β/ν=0.32± 0.05 and γ/ν=1.86± 0.15, respectively. These estimates result in a nontrivial dynamical critical exponent, z=0.50± 0.25.
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Yoshiaki Tanaka
Subject area: Statistical physics and thermodynamics.
1997 Volume 66 Issue 9 Pages
2647-2654
Published: September 01, 1997
Released on J-STAGE: October 01, 1999
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For the Ising model on the two-dimensional lattice with M× N lattice sites (M is a finite number; N→ ∞ ), a new method is presented by which the two-spin correlations at arbitrary distances are evaluated exactly. We make use of spinor analysis, which was employed by Kaufman and Onsager. The zero-field magnetic susceptibility χ
0 that is equal to the sum of all the two-spin correlations, is calculated.
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Yosuke Yoshimura
Subject area: Statistical physics and thermodynamics.
1997 Volume 66 Issue 9 Pages
2655-2664
Published: September 01, 1997
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Statistical thermodynamics of a spherical phantom molecule in a hard sphere fluid is studied. A phantom molecule has no interaction with solvent molecules at the ground state, but will have an interaction when excited. It is shown that the thermodynamical properties of the phantom molecule are closely related to the fluctuation of the solvent molecules in a finite region. Rigorous expressions are given at the small and large (continuum) limits. Thermodynamical properties of the phantom molecule of an intermediate size are demonstrated by using a Monte Carlo technique. The mean field approximation is invalid for a small phantom molecule and/or at low densities, although that works well for a large phantom molecule at high densities.
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Yuki Kato, Makoto Okamura, Masayuki Oikawa
Subject area: Fluid dynamics.
1997 Volume 66 Issue 9 Pages
2665-2674
Published: September 01, 1997
Released on J-STAGE: October 01, 1999
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Three systems of weakly nonlinear envelope equations for a fundamental mode and its fourth harmonic of two-dimensional capillary gravity waves on deep water are derived. These systems are used to investigate stability of progressive periodic waves of permanent form. It is found that the permanent waves in which the fundamental mode and its fourth harmonic are of the same order are unstable. Modulational instability in which the dominant mode in the eigenfunction is near the fourth harmonic is found in the third order approximation. Furthermore, instability related to the fourth harmonic resonance is found in the fourth order approximation.
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Yuki Kato, Makoto Okamura, Masayuki Oikawa
Subject area: Fluid dynamics.
1997 Volume 66 Issue 9 Pages
2675-2681
Published: September 01, 1997
Released on J-STAGE: October 01, 1999
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Three-dimensional instabilities of two-dimensional periodic capillary gravity waves of permanent form near the fourth harmonic resonance are investigated numerically. It is confirmed that the unstable regions appear in the neighborhood of the linear resonance curves of sum interactions associated with a fundamental mode and its fourth harmonic. No unstable regions overlap in the wave number plane of disturbances. Two regions are frequently reconnected.
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Takeshi Miyazaki, Kazuki Hirahara, Hideki Hashimoto
Subject area: Fluid dynamics.
1997 Volume 66 Issue 9 Pages
2682-2688
Published: September 01, 1997
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A family of exact stationary solutions of the Euler equations is presented. They are the generalizations of the Moore-Saffman vortex to N confocal ellipses that are embedded in a uniform background strain field e and a uniform background vorticity field 2γ . The two-dimensional linear instability of double ellipses is studied following Love, Moore & Saffman and Polvani & Flierl. Two types of instability are found. The first is the Love-type instability of the inner ellipse, which destabilizes an elliptical vortex patch whose aspect ratio is greater than 3. The second is the Rayleigh-type instability that occurs for concentric vortex patches with non-monotonic vorticity distribution.
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Takashi Aoyagi, Masatoshi Yagi, Sanae –I. Itoh
Subject area: Fluid dynamics.
1997 Volume 66 Issue 9 Pages
2689-2701
Published: September 01, 1997
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The Lorenz model for Rayleigh-Bénard convection is extended to the five components model taking an autonomous shear flow effect into account. The five components model is numerically solved and analyzed in detail. Based on the Lyapunov exponent analysis , how the introduction of the new degrees of the freedom (the shear flow) changes the chaotic behavior of the solution is examined. The attractors, the time evolutions, the power spectra, the Nusselt number of the five components model are compared with those of the Lorenz model. It is found that the solutions of both models converge to the same one when the Rayleigh number is small. When the Rayleigh number exceeds a critical value, the difference between the Lorenz model and the five components model is observed, i.e., the former has only the periodic solutions, while the latter contains the chaotic solutions. Some examples are shown. The limitation to a model with a few degrees of freedom is also discussed.
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Yuji Kurimoto, Hideki Zushi, Fumimichi Sano, Katsumi Kondo, Toru Mizuu ...
Subject area: The physics of plasmas and electric discharges.
1997 Volume 66 Issue 9 Pages
2702-2714
Published: September 01, 1997
Released on J-STAGE: October 01, 1999
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The inward shift and the toroidal precession of the deeply trapped ion orbit in Heliotron E plasmas are measured using the charge exchange analysis, and found to be consistent with the classical drift orbit theory. Depletion structures on energy spectra are observed during limiter insertion or pellet injection. Furthermore, the rapid change of the depletion structures by additional beam injection or limiter bias is also investigated. These depletion structures can be explained by an effect of the resonant loss due to the negative radial electric field, E
r. Theoretical analysis of the E
r profile shows that a positive E
r in the vicinity of the loss boundary disturbs the resonant condition of deeply trapped particles locally, and can reduce the resonant loss cone.
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Miho Motoyama, Takao Ohta
Subject area: Equations of state, phase equilibria, and phase transitions.
1997 Volume 66 Issue 9 Pages
2715-2725
Published: September 01, 1997
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We study morphology of chemically reacting binary mixtures quenched into a thermodynamically unstable region.One of the characteristic features of the system which has not been studiedso far is that one can change the average volume fraction during the phase separation process.Computer simulations are carried out in two dimensions to show a rich variety of stable domain morphologies.
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Takashi Itoh, Hiroya Ishikawa, Masato Hashimoto
Subject area: Equations of state, phase equilibria, and phase transitions.
1997 Volume 66 Issue 9 Pages
2726-2731
Published: September 01, 1997
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Temperature dependence of crystal structure and specific heat (C
p) is measured at normal pressure for solution-grown or as-synthesized nylon 6Y (Y=2, , 6, , 8, , 9, , 10, , 12) as well as nylons 6, 46 and 39. The first-order phase transition occurs in the as-synthesized nylon 62 crystal. Anomaly in C
p is observed for all even-even nylon 6Y, while any anomaly in C
p does not appear in nylons 46 and 6. Such results indicate that hexamethylene moiety plays an intrinsic role to cause the phase transition. The phase transition behavior tends to turn into the continuous structural change with increasing the number of Y in even-even nylon 6Y crystals, which suggests that thermal motion in the Y region expands the intermolecular distance to reduce the transition point to a temperature below 470, K and smear the phase-transition appearance.
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Sergey V. Dmitriev, Takeshi Shigenari, Kohji Abe
Subject area: Equations of state, phase equilibria, and phase transitions.
1997 Volume 66 Issue 9 Pages
2732-2736
Published: September 01, 1997
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Influence of the external pressure on the commensurate-incommensurate (IC) phase transition was studied in the frame of the elastically hinged molecule model of crystal which was recently proposed by the present authors. The case of compressible but rather hard molecules was treated.
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Kenichiro Yagi, Shigetada Shima, Hikaru Terauchi, Takasuke Matsuo
Subject area: Equations of state, phase equilibria, and phase transitions.
1997 Volume 66 Issue 9 Pages
2737-2740
Published: September 01, 1997
Released on J-STAGE: October 01, 1999
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An X-ray diffraction study of a clathrate compound, (thiourea)
3-CCl
4, was performed to elucidate the mechanism of phase transitions which are characterized by the orientational ordering of CCl
4 molecules. A discontinuous change of lattice constants was observed at (39±2) K indicating the second-order phase transition and a continuous change at (64±2) K, the first-order one. Below the upper transition temperature, the space group of the lattice changed from R3c to Cc. The lower two phases belong to the same space group Cc, though the phase transition occurred. The orientation of CCl
4 molecules deduced from the structural symmetry agrees with that proposed from the previous heat capacity and NQR measurements.
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Takeo Takagi
Subject area: Quantum fuids and solids: liquid and solid helium.
1997 Volume 66 Issue 9 Pages
2741-2746
Published: September 01, 1997
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A texture and a NMR spectrum of a superfluid
3He droplet are studied. The case of a droplet radius smaller than a dipole coherent length is considered. A l-texture of the droplet varies from half-disgyration, to relaxed monopole and finally it becomes boojum as the droplet growing. The boojum texture is determined under a dipole unlocked situation. The longitudinal, transverse and pulsed NMR frequencies of each texture are evaluated. We should be able to identify the droplet radius and the nucleation process of the superfluid
3He with these results.
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Junji Ohgami, Yasuhiro Sugawara, Seizo Morita, Toru Ozaki
Subject area: Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties).
1997 Volume 66 Issue 9 Pages
2747-2750
Published: September 01, 1997
Released on J-STAGE: October 01, 1999
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On a cleaved (010) surface of ferroelectric (NH
2CH
2COOH)
3· H
2SO
4 (TGS), time evolution of round islands with height corresponding to one chemical unit of TGS has been investigated using an atomic force microscope (AFM) in air at room temperature. The time evolution of the round islands at the measured humidity was characterized by a critical radius r
c of the island as follows. In case of an island with a radius r
c, the radius decreased and the island disappeared. On the other hand, in case of r>rc, the radius increased or was almost unchanged. The critical radius rc increased with an increase of the relative humidity. The relative humidity is associated with adsorbed water. These results are discussed with respect to a basic theory of growth of a two-dimensional nucleus in supersaturated aqueous solution.
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Tamio Oguchi, Noriaki Hamada
Subject area: Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties).
1997 Volume 66 Issue 9 Pages
2751-2757
Published: September 01, 1997
Released on J-STAGE: October 01, 1999
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The c(2×2) structure observed for Li-atom adsorbed Cu (001) surface at a low temperature is studied based on first-principles electronic structure calculations. Structural optimization is carried out with an LAPW atomic force method. Several numerical checks are done for better-known clean Cu (001) surfaces. Calculated total energies as well as vibration frequencies strongly support hollow-site adsorption in this system. Chemical bond formation is found between Li and Cu surface atoms, resulting a dipole polarization around Li. Rumpling relaxation found in atop-site adsorption may be a clue for understanding of stable atop configuration observed in Cs adsorption on Cu (111).
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Shoji Akazawa, Jun–ichiro Inoue, Sadamichi Maekawa
Subject area: Electron states in condensed matter.
1997 Volume 66 Issue 9 Pages
2758-2763
Published: September 01, 1997
Released on J-STAGE: October 01, 1999
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Motion of a single carrier added into a two-dimensional antiferromagnetic state is studied by using a variational method for a spin-fermion model which includes Coulomb interaction between itinerant fermions, antiferromagnetic coupling between localized spins, and Hund coupling between localized and itinerant spins. When the carrier is an electron at low density, the band-width representing the coherent motion of the carrier is similar to that of non-interacting electrons. On the other hand, when the carrier is a hole introduced into a half-filled band, it couples with the antiferromagnetic spin fluctuation, thereby the band-width of the coherent state becomes narrow and its lowest energy state appears at k=(π /2, π /2) for a square lattice. The results indicate that the dynamics of the carrier is strongly dependent on the type of carriers.
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Akiko Ishiguro, Hidekazu Aoki, Osamu Sugie, Michiro Suzuki, Anju Sawad ...
Subject area: Electron states in condensed matter.
1997 Volume 66 Issue 9 Pages
2764-2769
Published: September 01, 1997
Released on J-STAGE: October 01, 1999
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The de Haas-van Alphen effect has been measured in a semimetallic compound USb from at temperatures down to 45 mK and in fields up to 13.5 T. The observed three kinds of signal branches indicate that there exist two sets of ellipsoidal Fermi surfaces with different sizes and one spherical Fermi surface. The measured effective mass ratios m
*/m_0 are in the range between 0.9 and 2.7.
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Seiya Kumada, Norio Kawakami, Ayao Okiji
Subject area: Electron states in condensed matter.
1997 Volume 66 Issue 9 Pages
2770-2776
Published: September 01, 1997
Released on J-STAGE: October 01, 1999
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We investigate physical properties in the low-density limit of skyrmion excitations in the system at the Landau level filling factor ν=1/odd. We derive the spin susceptibility and the effective interaction between skyrmions beyond the mean field (saddle-point) approximation. Our approach consistently reproduces the spin susceptibility with the maximum structure at a finite temperature. We also find that the interaction is screened by thermally activated skyrmion-antiskyrmion pairs, whose spectra are concentrated in the low frequency regime around ω=Γ
q -- q
2, where Γ
q is the relaxation rate. It is shown that the skyrmion excitations reduce the magnetization and that the amount of the reduction in the magnetization due to the skyrmion excitations becomes small when we introduce the interaction between skyrmions.
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Yasunori Kubo, Yoshiharu Sakurai, Yoshikazu Tanaka, Tetsuya Nakamura, ...
Subject area: Electron states in condensed matter.
1997 Volume 66 Issue 9 Pages
2777-2780
Published: September 01, 1997
Released on J-STAGE: October 01, 1999
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The full-potential linearized augmented-plane-wave (FLAPW) method is employed to find out effects of introducing the self-interaction correction (SIC) on the band structures, electron wavefunctions and Compton profiles of both diamond and silicon. To examine the computed results high-resolution Compton profiles of silicon along the ‹ 100›, ‹ 110› and ‹ 111› directions are measured. In the case of silicon, it is found that theoretical Compton profiles computed with the SIC are in better agreement with the measured profiles when their first derivatives are compared. Although the effects of the SIC is much larger in the case of diamond, the theoretical prediction is to be tested by future high-resolution Compton profile measurements.
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Tetsuya Mutou, Hideaki Takahashi, Dai S. Hirashima
Subject area: Electron states in condensed matter.
1997 Volume 66 Issue 9 Pages
2781-2789
Published: September 01, 1997
Released on J-STAGE: October 01, 1999
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We study the formation of itinerant electronic states on carrier doping in a strongly correlated insulator by calculating one-particle-excitation spectral functions. We apply (1) the quantum Monte Carlo method and (2) the exact diagonalization method in the framework ofthe dynamical mean field theory to a two-band Hubbard model.The parameters of the model are chosen so that the undoped system is a charge-transfer-type insulator.We find that the itinerant states originate from localsinglet states formed by hybridized d- and p-holes.We also find asymmetry between hole-doped and electron-dopedcases: (1) in the electron-doped case a peak is not observed at the chemical potential in contrast to the hole-dopedcase; and (2) the mass-enhancement factor in the electron-doped caseis smaller than that in the hole-doped case.The results of the one-particle-excitation spectrum andthe mass-enhancement factor are discussed in the light ofexperimental and theoretical results for high-T
ccuprates.
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Junichi Okada, Yoshihiro Kuroda
Subject area: Electronic transport in condensed matter.
1997 Volume 66 Issue 9 Pages
2790-2797
Published: September 01, 1997
Released on J-STAGE: October 01, 1999
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By using the closed-form solution of the Mori formula for transport coefficients obtained very recently, the Mori formula and the Kubo formula have been proved to be identical to each other formally. However, once any approximation procedure is introduced, there may appear some discrepancy between these formula. Then, as for typical examples, we calculate the Mori formula and the Kubo formula for the optical conductivity in a free electron system with impurity scattering and for that in a U-infinite d-p model in some approximate ways and show that both formula coincide with each other practically and the memory function approximation which has been often employed as one of the most important applications of the Mori formula is justified only in the high frequency limit. These results suggest that the Mori formula is no more convenient to be used for calculating transport coefficients than the Kubo formula.
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Naoshi Takahashi, Shin–ichiro Tanaka, Masatake Ichikawa, Yong Q. ...
Subject area: Electronic structure and electrical properties of surfaces, interfaces and thin films.
1997 Volume 66 Issue 9 Pages
2798-2804
Published: September 01, 1997
Released on J-STAGE: October 01, 1999
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The electronic states of O/Cs/GaAs(100) have been investigated by using ultraviolet photoelectron spectroscopy in order to understand the initial coadsorption kinetics on the way to the negative electron affinity formation. It was found that the energy positions of the Ga-3d and As-3d peaks shift to the lower binding energy side by the first Cs deposition, while they shift to the higher binding energy side during the n-th Cs deposition (n≥3). It was also found that besides the appearance of oxidized As, the width of the Ga-3d peak becomes larger by the first oxygen exposure. In the case of the n-th Cs deposition and oxygen exposure, all photoelectron peaks and the work function made parallel shifts in energy, which can be well interpreted in terms of the change in band bending. These results indicate that the coadsorption kinetics can be classified into two stages: At first Cs deposition and oxygen exposure, both of Ga and As react with Cs and O, resulting in the rearrangement in the surface layers, while at n-th Cs deposition and oxygen exposure, surface layers or clusters consisting of Cs, O, As and Ga atoms are produced.
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Hiroki Tsuchiura, Hideaki Kasai, Ayao Okiji
Subject area: Electronic structure and electrical properties of surfaces, interfaces and thin films.
1997 Volume 66 Issue 9 Pages
2805-2810
Published: September 01, 1997
Released on J-STAGE: October 01, 1999
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A model calculation is presented for photo-stimulated desorption of adsorbates from a metal surface. In the model, the electron system of the material is described by a two-band tight-binding Hamiltonian. Interband electronic excitation is induced by laser pulse irradiation and causes a change in adsorbate trajectory. Close investigations are made of the dependence of the adsorbate trajectory on the photon energy and the time-width of laser pulse within one-photon process. For that purpose, an effective excited-state potential for adsorbate motion is introduced tentatively. When the electronic excitation is spatially localized in the neighborhood of the surface, substantial deviation of shape from the ground state potential can be seen in the effective excited-state potential, and gives rise to adsorbate desorption. It can be expected from the obtained results that the desorption probability increases as the photon energy is increased and as the time-width of laser pulse is decreased.
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Munehiro Azami, Tamifusa Matsuura, Yoshihiro Kuroda
Subject area: Superconductivity.
1997 Volume 66 Issue 9 Pages
2811-2819
Published: September 01, 1997
Released on J-STAGE: October 01, 1999
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Effective pairing interaction and superconducting transition temperature T
c are investigated on the basis of the simplest d-p model by using the auxiliary particle method together with the 1/N-expansion theory.The pairing interaction mediated by both charge and spin fluctuations is calculated by considering higher order terms in the 1/N-expansion within the random phase approximation(RPA) to find that it is attractive only for the d
x2-y2 channel.T
c is calculated by solving a linearized Eliashberg equation to confirm that it can be finite only for d
x2-y2 pairing.Doping dependence of T
c seems to be consistent with experiments with a reasonable choice of the parameter for the charge-transfer energy.The highest T
c is obtained at a hole-doping rate δ=0.15 and estimated to be ~= 100 K.It is also shown that the spin fluctuation plays a dominant role in the system to realize the high-T
c superconductivity rather than the charge fluctuation does.
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Kaoru Awaka, Hidetoshi Fukuyama
Subject area: Superconductivity.
1997 Volume 66 Issue 9 Pages
2820-2835
Published: September 01, 1997
Released on J-STAGE: October 01, 1999
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Effects of low energy excitation on the dynamics of Josephson phase in SNS junction are investigated. From the microscopic Hamiltonian, the effective action for the phase variable is derived. The retardation effects due to low energy excitation in normal (N) region are seen to play important roles in the dynamics of the phase. By the self-consistent harmonic approximation, renormalization of mass and dissipation constant are calculated, revealing the enhancement of the former and the suppression of the latter in general. Various situation appears depending on these renormalized values.
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Chitoshi Yasuda, Akihide Oguchi
Subject area: Magnetic properties and materials.
1997 Volume 66 Issue 9 Pages
2836-2843
Published: September 01, 1997
Released on J-STAGE: October 01, 1999
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Considering the reduction effect of the number of magnetic atoms and using Kondo and Yamaji's method and the coherent potential approximation, we investigate magnetic properties of a spin 1/2 Heisenberg antiferromagnet with nonmagnetic impurities on a square lattice. It is found that the critical impurity concentration x
c is different from the percolation threshold x
p in the ground state. The ground state changes from the Néel ordered state to a disordered state at x
c~= 0.07. The coherent exchange integral J
p vanishes at x
p~= 0.56. For 0≤ x
c the system is in the ordered state and for xcp in the disordered state. This disordered state is characterized by the finite Jp and energy gap and the exponentially decaying correlation function. This result explains that the reduction rate of the Néel temperature of Mg-doped La_2CuO_4 is larger than that of K_2CoF_4 and K_2MnF_4. The uniform susceptibility as a function of temperature and concentration is obtained.
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Masashi Kosaka, Hideya Onodera, Kenji Ohoyama, Masayoshi Ohashi, Yasuo ...
Subject area: Magnetic properties and materials.
1997 Volume 66 Issue 9 Pages
2844-2850
Published: September 01, 1997
Released on J-STAGE: October 01, 1999
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The magnetic properties of TmCu
2Si
2 are studied by magnetometric measurement, inelastic neutron scattering (INS) experiment, elastic constant measurement using ultrasonic velocity and neutron diffraction experiment on the powdered and single crystalline samples. Crystalline electric field (CEF) parameters which are determined by the magnetic susceptibility and the INS spectrum give 4f CEF levels consisting of a singlet Γ
3(1) ground state, a singlet Γ
4(1) first excited state at 6.1 K, a doublet Γ
5(1) second excited state at 79.5 K, and so on. Temperature variation of the 4f CEF level population, especially that of doublet Γ
5(1), explains well anomalous behavior of the magnetic susceptibility along the a-axis exhibiting the minimum around 15 K and the maximum around 45 K. Weak lattice softening below 120 K is also attributable mainly to strain susceptibility of Γ
5(1). An exchange-induced Van Vleck antiferromagnetic transition occurs at 2.8 K, since magnitude of transition probability between the ground Γ
3(1) and excited Γ
4(1) singlets is so large to induce the magnetic transition. It is confirmed that the antiferromagnetic structure is a sinusoidally moment-modulated one described by a propagation vector of q = (δ, δ, 0) with δ=0.147, where the Tm moments align along the c-axis.
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Kazuyuki Matsuhira, Toshiro Sakakibara, Hiroshi Amitsuka, Kenichi Teny ...
Subject area: Magnetic properties and materials.
1997 Volume 66 Issue 9 Pages
2851-2863
Published: September 01, 1997
Released on J-STAGE: October 01, 1999
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In order to study the single-site and inter-site effects in CeRu
2Si
2, a systematic diluting experiment has been performed with the single crystals of pseudo-ternary alloys Ce
1-x(La
0.63Y
0.37)
xRu
2Si
2 [0≤ x≤ 1], where the unit cell volume is kept unchanged to avoid the chemical pressure effect. Magnetization process in fields H≤ 200, kOe and at applied pressures P≤ 5, kbar, specific heat C(T), electrical resistivity ρ (T) and thermal expansion have been measured at temperatures above 1.5, K, with a special attention being paid to the metamagnetic behavior inherent in CeRu
2Si
2. In a whole Ce concentration range, the system remains in a non-magnetic state. Sharp metamagnetism shows a rapid broadening with x, and disappears at x-- 0.2 where incoherent Kondo scattering becomes significant in ρ (T). By careful analysis of single-site contributions, a peak structure is revealed in C(T) which is not explained by the “Kondo peak” alone. The result can be interpreted by a pseudo-gap in the quasi-particle band, which disappears upon dilution. Constant-volume magnetization process M
V(H) is derived from the measured zero-pressure curves, using the scaling hypothesis proved by the high-pressure experiment. Metamagnetism, although becoming much less sharp, still exists in M
V(H), indicating importance of an intrinsic mechanism other than the volume effect.
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