-
Kimiaki Konno, Hitoshi Oono
Subject area: Mathematical methods in physics.
1994 Volume 63 Issue 2 Pages
377-378
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
New coupled integrable dispersionless equations are presented and solved by the inverse scattering method.
View full abstract
-
Hiroyasu Yamada, Kazuhiro Nozaki
Subject area: Classical and quantum physics: mechanics and fields.
1994 Volume 63 Issue 2 Pages
379-382
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
The motion of untwisted scroll rings in excitable media is investigated with an approximation analysis. Application of the multiscale expansion technique yields slow dynamics of scroll rings without a quasi-stationarity assumption. Our formulation gives not only the shrinking rate and drifting speed of scroll rings but also new results such as a frequency shift of rotation and a slow deformation of the meridian spiral.
View full abstract
-
Zi–Song Hu, Kengo Takahashi, Yoshimi Tsuchiya
Subject area: Mechanics, elasticity, and rheology.
1994 Volume 63 Issue 2 Pages
383-387
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
Transient behaviors in self-sustained oscillation of a plasmodial strand of Physarum polycephalum have been investigated for various external loads under isotonic conditions. Synchronization between divisions of the strand has been observed in its formation process, which shows that the plasmodial strand can be considered as a one-dimensionally coupled oscillator system. The synchronization has been found to proceed faster with increasing external load applied to the strand. It has furthermore been found that the rate of increase of the amplitude of oscillation increases with the load, whereas the temporal behavior of its period is independent of the load. These results show that the oscillators themselves in the plasmodial strand do not depend on the external load, but the coupling between these oscillators is strongly affected with the external load. The experimental results have also been simulated on the basis of one-dimensionally coupled van der Pol equations.
View full abstract
-
Takashi Ishihara, Yukio Kaneda
Subject area: Fluid dynamics.
1994 Volume 63 Issue 2 Pages
388-392
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
The three-dimensional motion of a flat uniform vortex sheet slightly perturbed initially in both streamwise and spanwise directions is studied on the basis of a Lagrangian representation of the motion. The vortex sheet at time t is represented as R(λ
1, λ
2, t)=(λ
1, λ
2, 0)+∑
n, mA
n, m(t), exp, i(nλ
1+mδ λ
2), where λ
1 and λ
2 are Lagrangian parameters in the streamwise and spanwise directions, respectively, and δ is the aspect ratio of the periodic domain of the disturbance. The behaviour of A
n, 0 and A
n, 1 is studied by an asymptotic analysis valid at large t. The analysis shows that singularity appears on the sheet at a critical time O(ln, (ε
1-1)), where ε
1 is the initial amplitude of the streamwise disturbance. The singularity is such that A
n, 0 behaves like n
-5/2 while A
n, 1 behaves like n
-3/2, for large n. The latter is associated with the vortex stretching intrinsic in three-dimensional dynamics of the sheet.
View full abstract
-
Isao Katanuma, Yasuhito Kiwamoto, Leonid G. Bruskin, Kiyoshi Yatsu, Te ...
Subject area: The physics of plasmas and electric discharges.
1994 Volume 63 Issue 2 Pages
393-396
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
The electrostatic potential profile around a magnetic mirror throat is studied. Bohm's criterion expresses the necessary condition for the formation of a stationary sheath in front of the absorbing wall. This condition, when applied to the mirror throat of a magnetic mirror, requires that the ion drift velocity flowing into the mirror throat from the confining region must exceed the ion sound velocity for the continuity of the potential. It is found, however, that the ionization around the mirror throat renders the potential continuous even with zero ion drift velocity.
View full abstract
-
Tadao Kasuya
Subject area: Electron states in condensed matter.
1994 Volume 63 Issue 2 Pages
397-400
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
The experimentally observed Hall mobility in SmB
6 is temperature- and sample-quality-independent in the temperature range where the gap is well established, while the relaxation time observed in the optical measurement increases with decreasing temperature. This discrepancy was solved in our proposed model. It is shown that the Hall constant sees essentially a large Fermi surface for monovalent metal and, for a constant Hall mobility, τ should increase as T
-0.5, in good agreement with the experimental result.
View full abstract
-
Tetsuro Saso, Takumi Hayashi
Subject area: Electron states in condensed matter.
1994 Volume 63 Issue 2 Pages
401-404
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
The magnetization curve of the infinite-dimensional Hubbard model is calculated by using the quantum Monte Carlo method. The calculated curve is essentially the same as that of the exact solution in one dimension and that of the Gutzwiller approximation, which suggests the same behavior in all the intermediate dimensions. Combined with the knowledge on the Anderson impurity, the change of the shape of the density of states of the Hubbard model under a magnetic field is discussed.
View full abstract
-
Hideo Yoshioka
Subject area: Electronic transport in condensed matter.
1994 Volume 63 Issue 2 Pages
405-408
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
Fluctuation of spin magnetic susceptibility √ ‹ δ χ
2S› in mesoscopic metals is discussed in comparison with that of orbital magnetic susceptibility √ ‹ δ χ
2L› }. It is found that a ratio √ {‹ δ χ
2S› /√ ‹ δ χ
2L› is independent of temperature and the boundary condition and has a magnitude of the order of (1/ε
Fτ )
2 which is much smaller than unity, ε
F and τ being Fermi energy and the relaxation time of the elastic scattering, respectively. Scattering dependent on electron spin (e.g., spin-orbit interaction or scattering by impurity spin in the glass state) are shown to suppress √ ‹ δ χ
2S› far more strongly than √ ‹ δ χ
2L› . The results indicate that the anomalously large fluctuation of the magnetic susceptibility compared to the average, which is expected to be observed experimentally, results from the orbital motion.
View full abstract
-
Akio Fukushima, Fumitoshi Iga, Isao H. Inoue, Keizo Murata, Yoshikazu ...
Subject area: Electronic transport in condensed matter.
1994 Volume 63 Issue 2 Pages
409-412
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
We report transport and magnetic properties for single-crystalline CaVO
3, which are seriously affected by oxygen off-stoichiometry. The electrical resistivity of a stoichiometric sample is well fit by the relation ρ =ρ
0+AT
2 in an extremely wide temperature range. Oxygen off-stoichiometry causes the systematic increment of both ρ
0 and A. Magnetoresistance data also change drastically due to the oxygen off-stoichiometry; the stoichiometric sample shows positive magnetoresistance with B
2 dependence, while a sample with a small number of oxygen vacancies shows an unusual negative magnetoresistance. Magnetic susceptibility of the latter sample shows Curie-Weiss behavior, while that of the former one shows Pauli paramagnetic behavior.
View full abstract
-
Naoto Nagaosa, Akira Furusaki
Subject area: Electronic transport in condensed matter.
1994 Volume 63 Issue 2 Pages
413-415
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
The tunneling through a potential barrier in a Coulomb gas confined in a quantum wire is discussed. The tunneling conductance g(T) at temperature T is found to be [g(T)∝exp, \left[ln, \frac{v
F}{WT}-\frac{2}{3r}, \left {\left(1+r, ln, \frac{v
F}{WT}\
ight)
3/2-1\
ight}\
ight], \
]where W is the width of the wire, v
F is the Fermi velocity, and r=(8/π
2)r
s=4e
2/π v
Fε
0 is the dimensionless mean separation between electrons.
View full abstract
-
Fumitaka Matsubara, Katsunori Morishita, Sakari Inawashiro
Subject area: Magnetic properties and materials.
1994 Volume 63 Issue 2 Pages
416-419
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
We study a dilute system of the classical Heisenberg spins coupled via the Ruderman-Kittel-Kasuya-Yoshida (RKKY) interaction just above its critical concentration of the ferromagnetic phase using a hybrid Monte-Carlo spin-dynamics method. We find for the first time in finite-range models that the system exhibits a reentrant phase transition from a ferromagnetic phase to a mixed phase of the ferromagnetism and the transverse spin glass.
View full abstract
-
Makoto Kaburagi, Takashi Tonegawa
Subject area: Magnetic properties and materials.
1994 Volume 63 Issue 2 Pages
420-424
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
Low-lying excited states as well as the ground state of the spin-1 antiferromagnetic Heisenberg chain with a spin-1/2 impurity are investigated by means of a variational method and a method of numerical diagonalization. It is shown that 1) the impurity spin brings about massive modes in the Haldane gap; 2) when impurity-host coupling is sufficiently weak, the phenomenological Hamiltonian used by Hagiwara et al. (Phys. Rev. Lett. 65 (1990) 3181) in the analysis of ESR experimental results for Ni(C
2H
8N
2)
2NO
2(ClO
4) containing a small amount of spin-1/2 Cu
2+ impurities is derived from a more realistic Hamiltonian, as far as the energies of the low-lying states are concerned; 3) the results obtained by the variational method are in semiquantitative agreement with those obtained by numerical diagonalization.
View full abstract
-
Masafumi Tamura, Hiroshi Sawa, Yoshiaki Kashimura, Shuji Aonuma, Reizo ...
Subject area: Magnetic properties and materials.
1994 Volume 63 Issue 2 Pages
425-428
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
Weak ferromagnetism has been found in (DBr-DCNQI)
2Cu below the Néel temperature, T
N=16, K. The remanent magnetization does not decrease with lowering temperature, which is in contrast to that observed for (DMe-DCNQI-d
8)
2Cu. The results suggest that the weak ferromagnetism is a universal feature of the antiferromagnetically ordered state of the DCNQI
2Cu system.
View full abstract
-
Masafumi Tamura, Hiroshi Sawa, Shuji Aonuma, Reizo Kato, Minoru Kinosh ...
Subject area: Magnetic properties and materials.
1994 Volume 63 Issue 2 Pages
429-432
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
Temperature dependence of magnetic susceptibility of Cu salt of DMe-DCNQI-α, α '-d
2 has been investigated over the temperature range of the metal-insulator-metal (M-I-M) reentrant transition. The insulating phase of this salt has been revealed to exhibit the same temperature dependence of susceptibility as that of the insulator phase of (DMe-DCNQI-d
8)
2Cu, which shows only a M-I transition. In the reentrant metallic phase, there is no sizable enhancement of susceptibility such as expected from the specific heat enhancement.
View full abstract
-
Koichi Nakamura, Yoshio Kitaoka, Kunisuke Asayama, Toshiro Takabatake, ...
Subject area: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
1994 Volume 63 Issue 2 Pages
433-436
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
Low-energy excitation in Kondo semiconductors CeNiSn and CeRhSb, has been investigated by the measurement of
119Sn and
123Sb nuclear spin-lattice relaxation rate, 1/T
1. From a T
3-like temperature dependence of 1/T
1 for both compounds, it has been intuitively concluded that the pseudo energy gap with the V-shaped structure is formed in the effective density of states for heavy quasi-particles. The band width of D=210, K and the pseudo energy gap of Δ=28, K in CeRhSb are almost two times larger than those of CeNiSn (D=140, K and Δ=14, K), respectively. Below 0.4, K and 0.8, K for CeNiSn and CeRhSb, respectively, the T
1T=const. behavior has been commonly observed in the two compounds, indicative of the presence of a residual density of states at the Fermi level. Impurities and/or imperfection in the samples easily mask the intrinsic V-shaped structure of the energy gap at very low temperatures.
View full abstract
-
Fuminao Shimizu, Takayuki Anzai, Hiroshi Sekiguchi, Masaaki Takashige, ...
Subject area: Dielectric properties and materials.
1994 Volume 63 Issue 2 Pages
437-440
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
Single crystals of K
2ZnI
4 with monoclinic Sr
2GeS
4 structure prepared by theBridgman method were investigated through DTA and dielectric measurements. Ferroelectric activity was found below 270, K, where the b-direction dielectric constant showed a sharp peak. The spontaneous polarization measured by the pyroelectric charge method was 0.32, μ C/cm
2 at 100, K. The dielectric constant also showed a small stepwise anomaly around 190, K.
View full abstract
-
Masaru Kasahara, Pho Kaung, Toshirou Yagi
Subject area: Optical properties and condensedmatter spectroscopy and other interactions of matter with particles and radiation.
1994 Volume 63 Issue 2 Pages
441-444
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
The linewidth of the internal mode ν
2 of SO
42- ion of the antiferroelectric K
3D(SO
4)
2 shows the anomalous broadening with lowering temperature near the phase transition point. The broadening is well explained by a mechanism resembling the motional narrowing phenomenon in the nuclear magnetic resonance theory. The characteristic time of the motion of deuteron in a hydrogen bond is estimated to be on the order of 10
-13, s.
View full abstract
-
Takao Yoshinaga, Tsunehiko Kakutani
Subject area: Mathematical methods in physics.
1994 Volume 63 Issue 2 Pages
445-459
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
In order to examine solitary and E-shock waves in a resonant system between long and short waves, a reduced set of ordinary differential equations (ODEs) are considered by a simple traveling-wave transformation. It is then shown that analytical solutions can be obtained systematically by means of the modified Hirota's method. A variety of numerical solutions including oscillatory solitary and E-shock waves are also found for various values of the parameters. In particular, characteristic properties of the solutions are examined for the case when the ODEs hold the Painlevé property. In this connection, integrability of the original partial differential equations (PDEs) in the nearly integrable region is discussed together with the Lyapunov exponent for the soliton-like solutions.
View full abstract
-
E. V. Krishnan
Subject area: Mathematical methods in physics.
1994 Volume 63 Issue 2 Pages
460-465
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
Travelling wave solutions for two nonlinear diffusion equations have been found by a direct method. A new equilibrium solution has been found for the diffusion equation u
t=(u
2)
xx+u(u-1)(α-u) and also a singular solution when α=0 in the equilibrium state using the properties of elliptic functions.
View full abstract
-
Fei Zhang, Yuri S. Kivshar, Luis Vázquez
Subject area: Mathematical methods in physics.
1994 Volume 63 Issue 2 Pages
466-471
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
Sotiton-impurity interactions in the systems where the topological solitons (kinks) possess internal oscillatory modes are studied analytically and numerically. Taking the well-known φ
4 model as a particular but rather general example, we demonstrate that the kink can resonantly pass two (or more) localized impurities due to excitation and deexcitation of its internal mode.
View full abstract
-
H. Khushnood, A. R. Ansari
Subject area: Specific reactions and phenomenology.
1994 Volume 63 Issue 2 Pages
472-477
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
The characteristics of short-short and short-long rapidity gap correlations in 50GeV π
--nucleus and 400, GeV proton-nucleus interactions have been investigated. Thedependence of the characteristics of clusters on the multiplicity of grey particles, N
g, has also been studied. The results reveal that the behaviour of the rapidity gap correlations and the average cluster size are not only independent of the size of the target nucleus but also do not depend on the identity and energy of the impinging hadron. However, the increasing value of the parameter R with increasing value of N
g and the energy of the projectile indicates the dominance of the short-short rapidity gap correlations over the short-long correlations.
View full abstract
-
Katsufusa Shoda, Osamu Sasaki, Kunikazu Takeshita, Tsutomu Taniuchi, H ...
Subject area: Nuclear reactions and scattering: specific reactions.
1994 Volume 63 Issue 2 Pages
478-484
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
Energy distributions of π
+ electroproduced on
6Li,
9Be and
28Si were measured at the electron energy of about 200, MeV. The photon difference method was applied to these (e, , π
+) spectra in order to extract the (γ, , π
+) cross sections. Present results and previously obtained data show considerable contribution from several discrete levels of the residual nuclei. The spin-isospin flip giant resonance in residual nuclei could be studied up to about 20, MeV residual excitation except in
6Li which showed a small quasi-free and/or continuum contribution. In
9Be and
28Si, the present results show giant resonances in the residual nuclei with a width of about 15, MeV in the gross shape.
View full abstract
-
Hiroshi Tanaka, Ludwig Boesten, Kunizo Onda, Osamu Ohashi
Subject area: Atomic and molecular collision processes and interactions.
1994 Volume 63 Issue 2 Pages
485-492
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
Elastic electron scattering spectra of C
60 in the vapor phase were recorded from 1 to 11.5, eV and scattering angles from 30° to 90°. Electron energy loss spectra are given for a loss from 1 to 55, eV at impact energies of 50 and 100, eV (5°). They confirm the known optically allowed transitions and resolve the ≈ 6, eV π -electron plasmon-peak at least into four steps at 5.8, 6.1, 6.3, and 6.5, eV. A small peak of width 2, eV has been found at 28.3, eV, the position of the “σ +π -plasmon” in solid films. Vibrational excitations were recorded at 7, eV for angles from 20° to 60° with a resolution of 34, meV and show two peaks at 0.06 to 0.11, eV and at 0.15 to 0.20, eV both of which contain optically forbidden transitions. The elastic DCS at 7, eV and a scattering angle of 30° is estimated to be of order 5× 10
-14, cm
2/sr.
View full abstract
-
Kazuo Sasaki, Ryou Ohya
Subject area: Fluid dynamics.
1994 Volume 63 Issue 2 Pages
493-499
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
Solitary-wave solutions are obtained numerically for the nonlinear Schrödinger equation with some additional terms, which describes the forced oscillation of certain surface waves on a fluid in a channel that is driven sinusoidally with time in a horizontal direction. The conditions on the drive amplitude and frequency necessary for the existence of solitary waves are determined.
View full abstract
-
Noboru Takimoto, Shinzi Yamamura, Kunio Funayama
Subject area: Fluid dynamics.
1994 Volume 63 Issue 2 Pages
500-509
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
A discussion is given on a 1/f filter, which outputs a 1/f noise as a response to the white noise. It is shown theoretically and experimentally that, under proper conditions, an incompressible viscous fluid serves as the 1/f filter. Stimulated by the previous finding due to Mandelbrot et al. that the earth's pole motion involves the 1/f noise, a spherical shell enclosing a fluid is set in rotation about its diameter by a fluctuating external torque with the white spectrum, and its angular velocity is measured. It is found that, under the conditions predicted by the theory, the angular velocity involves the 1/f noise.
View full abstract
-
Akio Fukuyu, Taxpolat Ruzi, Akimitsu Kanai
Subject area: Fluid dynamics.
1994 Volume 63 Issue 2 Pages
510-527
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
The response of Hill's vortex to a small three dimensional disturbance is examined. The perturbed field is expanded by the spherical solid harmonics Y
nm and a system of equations for the evolution of the expansion coefficients is obtained. It is shown that these equations are closed for each azimuthal number m. In a case of axisymmetric distortion, Moffatt and Moore (1978) showed that if the initial disturbance is such as to make the vortex prolate spheroidal, rotational fluid is detrained, forming a thin spike at the rear stagnation point, and if the vortex is initially oblate, irrotaional fluid is entrained there. When the initial distortion is not axisymmetric, numerical results for m=2 show that a peak of initial surface elevation moves downstream toward the rear stagnation point forming a spike-like structure.
View full abstract
-
Jun Sang Park, Jae Min Hyun
Subject area: Fluid dynamics.
1994 Volume 63 Issue 2 Pages
528-535
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
Time-dependent motions of a compressible fluid in response to an abrupt rotation of the cylindrical container are considered. Concern is directed to the case of a rapidly-rotating cylinder; the reference Ekman number, E, is very small and the peripheral Mach number M≈ O(1). Numerical solutions to the complete Navier-Stokes equations are secured to appraise the relative importance of the major dynamical ingredients in the flow process. These endeavors are complementary to earlier works which demonstrated the global evolution of the dominant velocity component. The magnitudes of the terms of the azimuthal momentum equation are evaluated to enable specific comparisons of the dynamics effects involved. At high Mach numbers, the oscillatory behavior of the main flow is shown to be attributable to thermo-acoustic modes. The radial density stratification is strengthened as the Mach number increases; because of this, the fluid in larger portions of the cylinder interior experiences rarefaction and cooling. The consequence turns up in the form of retardation of the overall spin-up process as M increases.
View full abstract
-
Nobuaki Ikuta, Hiroaki Gotoda, Ryuichi Yokoyama
Subject area: Kinetic and transport theory of fluids; physical properties of gases.
1994 Volume 63 Issue 2 Pages
536-545
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
Electron velocity distribution and transport properties under an electric field have been analysed by the Boltzmann equation giving the flow-in rate with a scalar number of the momentum transfer collision frequency ν
m(v). This is equivalent to treat electrons as if they are isotropically scattered with ν
m(v) in spite of the fact being anisotropically scattered. Maintaining the momentum transfer cross section constant with the change of anisotropy in the elastic scattering, the validity of such pseudo-isotropic analyses has been examined by the extended FTI method assuming a simple model anisotropy. The results show that the transverse diffusion coefficient take erroneous values in the usual pseudo-isotropic analyses so far conveniently used.
View full abstract
-
Yoshiomi Kondoh, Yasuo Hosaka, Jia–Ling Liang, Ritoku Horiuchi, ...
Subject area: Kinetic and transport theory of fluids; physical properties of gases.
1994 Volume 63 Issue 2 Pages
546-557
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
Functional dependence of relaxed states of magnetohydrodynamic (MHD) plasmas on profiles of resistivity η is derived approximately as μ
0j
//~= √ μ
0α /2η B for parallel components to B, by using a general self-organization theory based on dissipative structures due to selective dissipations associated with higher eigenmodes for dissipative dynamic operators. Typical results of three-dimensional simulations for resistive MHD plasmas with both “nonuniform η ” and “uniform η ” are shown to compare with the theoretical result. Comparison between the theoretical and the numerical results suggests that the attractor of dissipative structures in resistive MHD plasmas is given by \
abla× (η j)=(α /2)B and is reduced to \
abla× B=λ B in the case with the “uniform η ” and no pressure gradient.
View full abstract
-
Yoshinori Tatematsu, Yasuhito Kiwamoto, Teruo Saito, Teruo Tamano
Subject area: The physics of plasmas and electric discharges.
1994 Volume 63 Issue 2 Pages
558-572
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
Theoretical analyses are made on the structure of the potential distribution along open field lines in a plasma where the velocity distributions of particles are modified from Maxwellian to include Yushmanov-trapped components and temperature anisotropy. The considered particle species are warm electrons and ions flowing out of the system, secondary electrons flowing backward, and Yushmanov electrons trapped between a stronger side of the magnetic field and reflecting potential. The analyses show systematic variations in the potential profile with the change in the temperature anisotropy and the abundance of the Yushmanov-trapped particles. Moreover, the analyses predict measurable feed-back effects to the local heating for the plasma control.
View full abstract
-
Mieko Toida, Yukiharu Ohsawa
Subject area: The physics of plasmas and electric discharges.
1994 Volume 63 Issue 2 Pages
573-582
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
Investigations are made of nonlinear magnetosonic waves propagating perpendicular to a magnetic field in a multi-ion plasma. The magnetosonic wave is split into two modes in a two-ion plasma; low- and high-frequency modes. The frequency of the low-frequency mode tends to zero as the wave number k goes to zero. A KdV equation is derived for this mode by the conventional reductive perturbation method. The frequency of the high-frequency mode does not tend to zero as k→ 0. Using a new expansion scheme in which the amplitude ε is assumed to be much larger than (m
e/m
i)
1/2, where m
e/m
i is a measure of electron-to-ion mass ratios, it is found that the nonlinear high-frequency mode can also be described by a KdV equation, although it has a finite cut-off frequency. This shows that KdV equations are not limited to the waves whose frequencies tend to zero as k→ 0.
View full abstract
-
Haruhiko Takase
Subject area: The physics of plasmas and electric discharges.
1994 Volume 63 Issue 2 Pages
583-592
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
The (1+2) dimensional (1-D in real space and 2-D in momentum space) relativistic Fokker-Planck code combined with the ray-tracing code has been newly developed for analyzing the lower hybrid current drive (LHCD) on tokamak plasmas. This numerical code calculates the 2-D MHD equilibrium, ray-tracing, and Fokker-Planck analyses self-consistently. The simulations have been carried out by using the code, and the results were compared with experiments on the lower hybrid current drive in JT-60. As a result, the obtained simulation results agreed with the experimental results on the current drive efficiency and the current density profile ( or the plasma internal inductance).
View full abstract
-
Shoji Hirokawa, Tomoko Imasaka, Takasuke Matsuo
Subject area: Equations of state, phase equilibria, and phase transitions.
1994 Volume 63 Issue 2 Pages
593-601
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
A system of planar rotators representing H
2S and D
2S molecules is investigated quantum-statistically, using the mean-field approximation based on an eight-sublattice model. The equilibrium molecular orientation is determined by competition among the dipole-dipole interaction between guest molecules, the host-guest interaction and the quantum kinetic energy. The system has a complex order parameter describing an average direction of dipoles. Both R1 and R3 structures and the effect of the depolarization field are studied. A comparison with experiment by use of theoretical phase diagrams gives: the low-temperature phase has the R1 structure with an antiferroelectric order of dipoles; the direction and arrangement of dipoles in equilibrium for H
2S significantly differ from those for D
2S because of the quantum nature of the rotational motion.
View full abstract
-
Fusayoshi J. Ohkawa, Naoyuki Matsumoto
Subject area: Electron states in condensed matter.
1994 Volume 63 Issue 2 Pages
602-614
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
The origin of the superexchange interaction is reexamined in order to clarify that it works even in metallic phases. The wellknown kinetic exchange process is nothing but the virtual exchange process of high-energy spin excitations between the lower and upper Hubbard bands. The mechanism for Cooper pairing between Gutzwiller's heavy electrons, whose band lies between the lower and upper Hubbard bands, by the superexchange interaction can be regarded as that by high-energy spin fluctuations. Because it can also be regarded as a kind of an excitonic mechanism using high-energy spin excitations, it is plausible that the superexchange interaction causes high-temperature superconductivity of Gutzwiller's heavy-electron liquids.
View full abstract
-
Masafumi Tamura, Haruo Kuroda, Shinya Uji, Haruyoshi Aoki, Madoka Toku ...
Subject area: Electron states in condensed matter.
1994 Volume 63 Issue 2 Pages
615-622
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
Analysis of the temperature and field dependence of the de Haas-van Alphen oscillations in an organic superconductor θ -(BEDT-TTF)
2I
3 is presented. The cyclotron masses are estimated to be 2.0m
e and 3.6m
e for slow and fast oscillations, respectively. The indication of magnetic breakdown effect is discussed in terms of the geometry of the Fermi surface. The result is compared with those of the infrared reflectance spectra and the empirical tight-binding band calculations.
View full abstract
-
Shintaro Nakamura, Terutaka Goto, Satoru Kunii, Katsuhiko Iwashita, Ak ...
Subject area: Electron states in condensed matter.
1994 Volume 63 Issue 2 Pages
623-636
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
Temperature dependence of the elastic constants in a series of rare earth hexaborides has been investigated by means of the ultrasonic method. The remarkable softening of the transverse C
44 mode in PrB
6, NdB
6, DyB
6 and HoB
6 has been discussed in connection with the cooperative Jahn-Teller effect due to the CEF ground state degenerated by the quadrupolar moment. The low temperature behavior of C
44 in Ce
xLa
1-xB
6 compounds is presented to show the Kondo effect on the quadrupolar moment of Γ
8 ground state. The anomaly of the bulk modulus C
B in SmB
6 is related to the valence fluctuation state in the system.
View full abstract
-
Hitoshi Sumi, Atsuko Sumi
Subject area: Electron states in condensed matter.
1994 Volume 63 Issue 2 Pages
637-657
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
Self-trapping (ST) of excitons (or electrons) interacting with phonons via short-range potentials depends strongly on the degree of freedom of their motion on the lattice. When excitons can move three-dimensionally, the self-trapped (S) state appears suddenly as a strongly-localized one when the coupling constant (g) exceeds a certain critical value. Free (F) states do not become unstable however large g is. When exciton motion is limited only in one dimension, excitons are always self-trapped and F states are unstable irrespective of the magnitude of g (≠ 0). The S state appears as a strongly-extended one in the limit of g→ 0, and its spatial extension decreases as g increases. For excitons mobile in two dimensions, there exist two critical values g
c1 and g
c2 (>g
c1) of g: The S state appears suddenly as a strongly-localized one when g exceeds g
c1, but F states become unstable when g exceeds g
c2 although they are metastable for g
c1c2.
View full abstract
-
Taichi Terashima, Norimichi Kojima
Subject area: Electronic transport in condensed matter.
1994 Volume 63 Issue 2 Pages
658-673
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
Incommensurate layer compounds (RES)
xNbS
2 are a new class of the intercalation compounds of NbS
2; the x=1.2 and the x=0.6 compound have a stage-1 and a stage-2 structure, respectively. The results of the resistivity and the Seebeck coefficient measurements for several of them and the Pauli paramagnetic susceptibility of (LaS)
1.2NbS
2 are well interpreted with the rigid-band model by incorporating a large charge transfer from the intercalate RES layer to the host NbS
2 layer. Large residual resistivities of the compounds are discussed in terms of the structural incommensurability. A logarithmic temperature dependence of the resistivity observed for the stage-2 compounds below -- 20, K is discussed in relation with the carrier localization. A fractional superconductivity has been observed for most of the samples below 2-- 6, K and its model based on the peculiar structure is proposed.
View full abstract
-
Yasuhiro Iye, Ryuta Yagi, Noriaki Hanasaki, Seiichi Kagoshima, Hatsumi ...
Subject area: Electronic transport in condensed matter.
1994 Volume 63 Issue 2 Pages
674-684
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
Angular dependent magnetoresistance oscillation (ADMRO) effect in α -(BEDT-TTF)
2MHg(SCN)
4 [M: K, , NH
4] has been studied as a function of the polar and azimuthal angles of applied magnetic field with respect to the most conducting ac-plane. The ADMRO effects in these two structurally similar compounds are drastically different in their azimuthal angle dependence and oscillation waveform. While the ADMRO in NH
4Hg-salt is of the standard type arising from a warped cylindrical Fermi surface, that in KHg-salt is a novel type to be attributed to an open Fermi sheet. Calculation based on a model recently proposed for a quasi one-dimensional system quantitatively reproduces the essential features of the anomalous ADMRO in KHg-salt.
View full abstract
-
Tomi Ohtsuki, Yoshiyuki Ono, Bernhard Kramer
Subject area: Electronic transport in condensed matter.
1994 Volume 63 Issue 2 Pages
685-694
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
The localization problem in a three dimensional tight binding system in the presence of a spatially random vector potential is investigated. The density of states exhibits tails of localized states that are induced by large regions in space where the vector potential is accidentally constant. In the center of the band the states are shown to be extended by investigating the system size dependence of the inverse participation number. The existence of a metal-insulator transition at a critical energy with non-vanishing density of states is demonstrated. The system size and energy dependent exponential decay length of the modulus of the Green's function satisfies a one-parameter scaling law. The value of the critical exponent is estimated, ν ≈ 1, which is different from those found previously for the disordered tight binding (Anderson) model with and without homogeneous magnetic field.
View full abstract
-
Hijiri Kito, Jun Akimitsu, Fujio Izumi, Takashi Kamiyama, Hajime Asano
Subject area: Superconductivity.
1994 Volume 63 Issue 2 Pages
695-699
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
The structure parameters of (La
1-xCa
x)
2CuO
4 (x=0.05) with the K
2NiF
4-type structure were refined by Rietveld analysis of time-of-flight neutron powder diffraction data. This superconductor with a T
c of 24, K is orthorhombic at both room temperature and 18, K. From experimental results obtained by us and Fukuoka et al., we conclude that the relatively low T
c value for the superconductor is due to a low concentration of hole carriers introduced by Ca doping.
View full abstract
-
Shigeki Ohsugi, Yoshio Kitaoka, Kenji Ishida, Guo–qing Zheng, Ku ...
Subject area: Superconductivity.
1994 Volume 63 Issue 2 Pages
700-715
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
Results of extensive Cu NMR and NQR studies in the superconducting La
2-xSr
xCuO
4 with x=0.075-- 0.24 have been presented. The rapid decrease of the nuclear spin-lattice relaxation rate, 1/T
1, and the spin Knight shift below T
c confirm microscopically the existence of the superconducting phase with lower T
c than 38, K for 0.10 ≤ x ≤ 0.24. For x=0.10, magnetic anomalies emerge at low-T in some small parts of the sample, e.g. T-independent T
1 and broadening of spectrum, having some relevance to the magnetic order in La
2-xBa
xCuO
4 with x=0.125. For x>0.15, the T
1T=const. behavior and the existence of the residual spin Knight shift far below T
c have revealed that the superconductivity is of a gapless type with a finite density of states at the Fermi level caused by the mixture of different structures, i.e. tetragonal and orthorhombic.
View full abstract
-
Shuzo Kawarazaki, Yutaka Kobashi, Toshifumi Taniguchi, Yoshihito Miyak ...
Subject area: Magnetic properties and materials.
1994 Volume 63 Issue 2 Pages
716-725
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
We have carried out neutron diffraction experiments in order to study on the intermediate phase of the mixed system, U(Ru
1-xRh
x)
2Si
2, of URu
2Si
2 and URh
2Si
2, which are a heavy Fermion and a localized f-electron compounds, respectively. In the intermediate phase, the magnetic moment of the uranium atom has a normal magnitude but the ground state has a complex multi-Q-domain structure. The origin of this state is discussed on the basis of competing anisotropic interactions and randomness in them. An energy-based consideration is given to understand the variation of the magnetic structures in U(Ru
1-xRh
x)
2Si
2 and Ce(Ru
1-xRh
x)
2Si
2 sytems.
View full abstract
-
Hiroyuki Kita, Andreas Dönni, Yasuo Endoh, Kazuhisa Kakurai, Nori ...
Subject area: Magnetic properties and materials.
1994 Volume 63 Issue 2 Pages
726-735
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
The magnetic phase diagram of the heavy fermion superconductor UPd
2Al
3 (T
N=14.3, K) has been determined in magnetic fields up to 5, Tesla by single crystal neutron diffraction experiments, which were performed at several temperatures above and below the superconducting transition at T
c=1.8, K. Observed magnetic intensities correspond to the magnetic structure with a field-independent magnetic propagation vector k=[0, , 0, , 1/2]. A magnetic field applied in the hexagonal a-b plane gives rise to domain reorientations, in addition rotates the direction of the ordered magnetic moments against a small anisotropy in the easy a-b plane, and makes the moment directions perpendicular to the field direction. This model allows a quantitative analysis of the observed field dependence of magnetic peak intensities. No superconductivity-induced changes of the antiferromagnetic order in UPd
2Al
3 are observed in our experiments. However, an anomaly detected in the temperature dependence of the zero-field sublattice magnetization for 11, K≤ T ≤ 14.3, K indicates a change in the magnetic structure of UPd
2Al
3.
View full abstract
-
Hiroshi Amitsuka, Toshiro Sakakibara
Subject area: Magnetic properties and materials.
1994 Volume 63 Issue 2 Pages
736-747
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
Specific heat C, electrical resistivity ρ, magnetization M and magnetic susceptibility χ have been measured for the dilute tetragonal heavy-electron compounds U
xTh
1-xRu
2Si
2 (x≤ 0.07), in the temperature range 100, mK≤ T≤ 360, K and in the magnetic fields H up to 55, kOe. Non-Fermi-liquid behavior with unusual lnT dependence of C, ρ and χ has been observed at the low temperatures: as the temperature is lowered below about 10, K, C/T and χ increase logarithmically, and ρ decreases logarithmically. Systematical variations of these quantities with uranium concentration indicate that the observed non-Fermi-liquid behavior is ascribed to the properties of a single U ion embedded in the Th site of the ThRu
2Si
2 metal. The magnetization curves M vs H/T indicate a strong uniaxial magnetic anisotropy along the tetragonal c-axis as well as a strong reduction of the 5f moment of U ions. A possible interpretation based on the recent developments of the S=1/2 two-channel Kondo model is given.
View full abstract
-
Akira Yazaki, Keisuke Tajima, Yoshiei Todate, Syoïchi Tomiyoshi, ...
Subject area: Magnetic properties and materials.
1994 Volume 63 Issue 2 Pages
748-754
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
Neutron paramagnetic scattering experiments have been made on antiferromagnets of RbMnF
3 and Mn
3Pt by means of Time of Flight (TOF) technique. The constant q mode data have been constructed by selecting the data points of the same q value from a set of TOF spectra. A simple Lorentzian scattering function has been assumed for the analysis and characteristic properties of the paramagnetic spin dynamics have been compared between these Heisenberg and metallic antiferromagnets.
View full abstract
-
Tôru Sakai, Minoru Takahashi
Subject area: Magnetic properties and materials.
1994 Volume 63 Issue 2 Pages
755-761
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
We study the spin-1 antiferromagnetic Heisenberg chain under the three boundary conditions, which are the free, periodic and antiperiodic boundary conditions, by numerical diagonalization up to 16 sites. We checked that the lowest excitation caused by the domain wall, which is imposed by the boundary condition and breaks the long-range string order, yields the same energy gap under all the boundary conditions in the infinite length limit. It is also found that the ground state and the first excited state have the same density (about 3%) of domain walls due to the quantum fluctuation which reduces the string order parameter about 10% smaller than that of the VBS model in the ground state. The analysis of the mean distance between two domain walls suggests that domain walls due to the quantum fluctuation form a bound state in pairs and does not break the long-range string order.
View full abstract
-
Hideki Watanabe, Eiichi Hirota, Akira Okada, Kouichi Hamada, Iwao Ishi ...
Subject area: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
1994 Volume 63 Issue 2 Pages
762-768
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
Ferromagnetic resonance (FRM) measurements were made on [Ni
0.8Fe
0.15Co
0.05/Cu/Co] multilayers in order to observe the coupling between ferromagnetic layers across Cu spacer. The resonant fields vary oscillatory with Cu spacer thickness. The FMR results were analyzed by the resonant model of a magnetically coupled two-layer system. By using a modified RKKY theory for interlayer exchange interaction and FMR results, the coupling constant, J, was determined as a function of Cu spacer thickness. The resonant field can be predicted for Cu spacer thickness and are well compared to the experimental values. In samples of antiferromagnetic coupling, the resonance mode of the magnetization flopping were observed at small applied fields.
View full abstract
-
Isayuki Horio, Xue–Zhi Zhou, Allan Henrry Morrish
Subject area: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
1994 Volume 63 Issue 2 Pages
769-774
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
The surface magnetic structure of γ -
56Fe
2O
3 acicular particles with and without adsorbed Co
2+ ions was investigated by coating with
57Fe
2+ ions and then employing Mössbauer spectroscopy. The samples were characterized by chemical analysis, transmission electron microscopy, X-ray diffraction and magnetic measurements. The Mössbauer spectra at room temperature consisted of a sextet with broad lines with tails towards zero velocity. At 4.2, K in an applied field of 50, kOe the spin structure is non-collinear especially for the samples with the adsorbed cobalt ions.
View full abstract
-
Yutaka Nakai
Subject area: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
1994 Volume 63 Issue 2 Pages
775-780
Published: February 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
RESTRICTED ACCESS
About 90% of Sn atoms in β -Mn structure are found by means of neutron diffraction to occupy site II and neither antiferromagnetic long range order nor remarkable short range order was observable. By Mössbauer spectroscopy of
119mSn, the magnitude of the electric field gradient (EFG) decreases with an increase in Sn concentration. The EFG distribution functions are expressed by the sum of two Lorentz distributions. From the stable distribution analysis of internal field distributions, it becomes clear that the magnetic moments randomly freeze in the noncollinear manner.
View full abstract