Journal of the Physical Society of Japan
Online ISSN : 1347-4073
Print ISSN : 0031-9015
ISSN-L : 0031-9015
Volume 62, Issue 11
Displaying 1-50 of 55 articles from this issue
  • Masaaki Tanaka, Takeshi Kawabe
    1993 Volume 62 Issue 11 Pages 3767-3770
    Published: November 15, 1993
    Released on J-STAGE: May 29, 2007
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    It is exhibited, for a complex logarithmic map (Remark: Graphics omitted.), that there exists a k-period region near the point with Ω=1⁄k on the boundary curve of the cycloid C=exp (i2πΩ)−i2πΩ where a Hopf bifurcation takes place, and that a circle map is embedded into the curve. The Devil’s staircase emerges just within the boundary and the Farey tree is constructed. The area of the k-period region in a periodic sequence 2→3→4→… is predicted to be scaled by k−6 for large k, and which is also numerically ascertained.
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  • Tohru Morita, Kazuyuki Tanaka
    1993 Volume 62 Issue 11 Pages 3771-3773
    Published: November 15, 1993
    Released on J-STAGE: June 01, 2007
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    It is shown that there exists a generalized Heisenberg model of half-odd-integral spin S greater than 1/2 corresponding to the model of spin 1/2, and we have exactly solved models of half-odd-integral spin S greater than 1/2 corresponding to exactly solved models of spin 1/2.
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  • Yoshihiko Nonomura, Masuo Suzuki
    1993 Volume 62 Issue 11 Pages 3774-3777
    Published: November 15, 1993
    Released on J-STAGE: June 01, 2007
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    A Kosterlitz-Thouless (KT)-type transition in the one-dimensional S=1⁄2 XXZ model at the ground state is analyzed using the double-cluster approximation (DCA) and the coherent-anomaly method (CAM). It is numerically shown that the periodic-boundary condition (PBC) is suitable for the construction of a systematic series of cluster approximations in quantum antiferromagnets. The transition point and the exponent of the essential singularity are estimated as gc*\simeq0.9969 and σ\simeq0.527, which are in good agreement with the exact values, gc*=1 and σ=0.5, respectively. Such accuracy of estimation is due to the consideration of a power-law factor in front of the exponential singularity of \barχ, which had been neglected until now.
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  • Kh. S. Singh, P. K. Choudhury, Vandana Misra, P. Khastgir, S. P. Ojha
    1993 Volume 62 Issue 11 Pages 3778-3782
    Published: November 15, 1993
    Released on J-STAGE: June 01, 2007
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    The boundary value problem of a parabolically bent planar waveguide that is completely filled with a homogeneous isotropic chiral material is solved and expressions for the field cutoffs are derived considering special cases. Results are expected to have application in the design of composite chiral media as well as in the tolerance study of planar chiroguides with curvature and flare. The presence of chirality in the cladding introduces some attenuated modes in the waveguide.
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  • Seigo Kishiba, Koji Ohkitani, Shigeo Kida
    1993 Volume 62 Issue 11 Pages 3783-3787
    Published: November 15, 1993
    Released on J-STAGE: June 01, 2007
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    A systematic method of estimating the degree of nonlocal dependence of the rate-of-strain tensor upon the vorticity is proposed and applied to a numerical simulation of decaying isotropic turbulence. Locality functions defined with a screened strain show similarity after vortex tubes are formed if the screening radius is normalized by the Taylor microscale λ. About 40% (50%) of energy dissipation (enstrophy production) comes from such regions where the distance from the point of source vorticity is larger than 2λ. A physical interpretation of this finding is made in connection with Tennekes’ model [Phys. Fluids 11 (1968) 669].
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  • Makoto Umeki
    1993 Volume 62 Issue 11 Pages 3788-3791
    Published: November 15, 1993
    Released on J-STAGE: June 01, 2007
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    The probability distribution functions (PDFs) of the circulation of velocity in three-dimensional decaying isotropic turbulence are examined using the database of numerical simulation based on the spectral method. It is shown that the standard deviation increases nearly as A2⁄3 where A is the area of the loop. The PDFs change from exponential to Gaussian as the size increases. The former agrees well with the prediction by Migdal (1993, hep-th/9303130), although the latter deviates from it. A modification is proposed to explain the Gaussian distribution with the A2⁄3 dependence.
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  • Iwao Hosokawa
    1993 Volume 62 Issue 11 Pages 3792-3796
    Published: November 15, 1993
    Released on J-STAGE: June 01, 2007
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    The multifractal nature of isotropic turbulence is revealed from the viewpoint of the d(h) spectrum for longitudinal velocity increment presumed by Frisch and Parisi, using the 3D binomial Cantor set model. The correctly applied Kolmogorov refined similarity hypothesis is found to play a vital role in construction of the rational d(h) spectrum in the entire range of h from the knowledge of the f(α) spectrum for three-dimensional dissipation field of turbulence. It is also shown that velocity increment is not scale-similar in a strict sense, in contrast to dissipation field averaged over the domain across which velocity increment is considered.
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  • Hitoshi Hojo, Ryota Katsumata, Makoto Ichimura, Masaaki Inutake
    1993 Volume 62 Issue 11 Pages 3797-3800
    Published: November 15, 1993
    Released on J-STAGE: June 01, 2007
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    The effect of end plugging of the ion on the Alfvén ion cyclotron instability in a mirror-confined plasma is studied. The dispersion equation in the uniform-plasma approximation is derived by assuming a loss cone distribution of the ion, taking into account the end plugging, and is solved numerically. It is shown that the end plugging effect of filling the loss cone mainly causes the reduction of the temperature anisotropy of the ion, leading to the suppression of the instability.
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  • Hirotaka Yamaguchi, Toshimitsu Ito, Kunihiko Oka, Haruhiko Obara
    1993 Volume 62 Issue 11 Pages 3801-3804
    Published: November 15, 1993
    Released on J-STAGE: May 29, 2007
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    Amorphization under pressure has been observed in CuGeO3 at room temperature. It is apparently revealed by the change in color from blue to green. The amorphous feature in the green-colored phase was demonstrated by X-ray diffraction measurement, in which the Bragg peaks almost disappeared and a halolike background is observed. An exothermic reaction due to crystallization was observed at about 580°C in the amorphous phase by differential thermal analysis. Antiferromagnetism in the crystalline CuGeO3 is replaced by Curie-paramagnetism in the amorphous one.
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  • Kazuo Gesi
    1993 Volume 62 Issue 11 Pages 3805-3808
    Published: November 15, 1993
    Released on J-STAGE: May 29, 2007
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    The composition (x)-temperature (T) phase diagram of N(CH3)4Mn1−xCuxCl3 solid solution has been studied through dielectric measurements. The I–II transition temperature (126 K for x=0) increases with increasing x. An intermediate phase (phase III) appears at about x=0.03, and its range expands as x increases further. The obtained x-T phase diagram closely resembles the pressure (p)-temperature (T) phase diagram of pure N(CH3)4MnCl3 reported previously.
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  • Kazuhiro Sano, Ken’ichi Takano
    1993 Volume 62 Issue 11 Pages 3809-3812
    Published: November 15, 1993
    Released on J-STAGE: June 01, 2007
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    We investigate the one-dimensional t-J-J′ model by the numerical diagonalization where a few holes are doped in the half-filled band. By introducing a finite-size scaling, we estimate the spin gap at J′⁄J=0.5 and Jt=2. When one hole is doped, the spin gap decreases to 0.190J in comparison with 0.236J which is the spin gap of the half-filled band. The spin gap further reduces to 0.141J for two-hole doping and to about 0.05J for three-hole doping. This result shows that the value of the spin gap as a function of the electron density is discontinuous at half-filling.
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  • Yoshiyuki Ono, Tomi Ohtsuki
    1993 Volume 62 Issue 11 Pages 3813-3817
    Published: November 15, 1993
    Released on J-STAGE: June 01, 2007
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    The spacing distributions of unfolded energy levels in the lowest Landau band formed in disordered two-dimensional electron systems are numerically studied for different energy regions. By fitting the distribution function to an appropriate interpolation formula, the level repulsion parameter β is obtained as a function of the unfolded energy x. The functional forms of β(x) for different system sizes are found to exhibit a certain scaling behavior. From this scaling property, it is possible to estimate the exponent of the localization length as a function of energy, which is found to be 2.4±0.2, consistent with previously reported values. Possible applications to other Anderson transitions are also discussed.
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  • Karel Vacek, Ayao Okiji, Norio Kawakami
    1993 Volume 62 Issue 11 Pages 3818-3821
    Published: November 15, 1993
    Released on J-STAGE: May 29, 2007
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    Conductance resonances in narrow channels of finite length are investigated theoretically. The electron-electron interaction is modeled by the 1⁄r2 interaction for the one-dimensional system confined with harmonic potential. We obtain the exact ground state for the model and calculate the resonant energies for the system weakly coupled to reservoirs. We find that the conductance displays resonances with two independent periods reflecting the infernal spin degrees of freedom.
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  • Yutaka Maniwa, Koichi Kikuchi, Takashi Higono, Atushi Ohi, Kiyoshi Kum ...
    1993 Volume 62 Issue 11 Pages 3822-3824
    Published: November 15, 1993
    Released on J-STAGE: June 01, 2007
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    Ternary-alkali-metal-intercalated fullerides, KRbCsC60, was prepared by method employing alkali metal azides reported by Bensebaa et al. (F. Bensebaa, B. Xiang and L. Kevan: J. Phys. Chem. 96 (1992) 6118). We found that KRbCsC60 is a superconductor with the transitipn temperature of 28(bulk)∼29 K (onset). It was also found, from nuclear magnetic resonance (NMR) study of 87Rb and 133Cs in this system, that the alkali atoms are site-selectively intercalated into C60 face-centered-cubic (fcc) lattice. The largest alkali-metal ion, Cs, occupies octahedral sites of the C60 fcc lattice, and the K and Rb atoms occupy mainly tetrahedral sites.
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  • Katsuma Yagasaki, Masato Hedo, Takao Nakama
    1993 Volume 62 Issue 11 Pages 3825-3828
    Published: November 15, 1993
    Released on J-STAGE: May 29, 2007
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    Magnetization curves [MC] and temperature dependence of the AC susceptibility [TS] were measured in the superconducting phase of CeRu2 with Tc=6.55 K in zero field. For fields higher than 0.8 T in [TS], the superconducting susceptibility behaves normally up to the lowest transition temperature TcL where it decreases suddenly; the field-induced reentrant superconductivity occurs at TcL and breaks very sharply to the normal state at TcH (the highest transition temperature). In [MC], an anomaly appears when the magnetization reaches to the extrapolated magnetization of the normal state at HR (reentrant field). Magnetization drops suddenly to negative in the field-increasing process for temperatures below 3.9 K, and it only increases for temperatures above 4.0 K. Reentrant superconductivity occurs between, HR and Hc2. The reentrant phase has positive magnetization in the background.
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  • Shunji Sugai
    1993 Volume 62 Issue 11 Pages 3829-3831
    Published: November 15, 1993
    Released on J-STAGE: June 01, 2007
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    Magnetic properties of CuGeO3 were investigated by Raman scattering. Broad two-magnon scattering extending over 2000 cm−1 develops below 200 K. This wide energy indicates that the spins are two-dimensional, that is, the interchain ferromagnetic exchange energy is ten times larger than the intrachain antiferromagnetic exchange energy. The two-dimensionality is against the current interpretation of the spin-Peierls transition. The intensity below 1000 cm−1, especially below 100 cm−1, decreases below 50 K due to the dimeric lattice distortion.
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  • Hironobu Ikeda, Kazuaki Iwasa, Ken H. Andersen
    1993 Volume 62 Issue 11 Pages 3832-3836
    Published: November 15, 1993
    Released on J-STAGE: June 01, 2007
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    The intensity distribution of the magnetic elastic scattering of neutrons near the superlattice position in two-dimensional diluted Ising antiferromagnets, Rb2CocMg1−cF4 (c=0.60, 0.65 and 0.70), reveals direct experimental evidence of the self-similarity of the magnetic order in a percolating magnetic system. The observed fractal dimension is 1.95±0.07, which is in accord with a numerically estimated value of 1.896. Evidence for a crossover from a self-similar fractal structure to a homogeneous structure is also presented.
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  • Takashi Nagatani
    1993 Volume 62 Issue 11 Pages 3837-3840
    Published: November 15, 1993
    Released on J-STAGE: May 29, 2007
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    A cellular automaton (CA) model is presented to simulate the clustering (or aggregation) process of cars in traffic flow on a highway. The CA model is an extended version of the one-dimensional asymmetric simple-exclusion model taking into account the variation of car velocity which depends on the distance between a car and the car ahead. Using computer simulation, it is found that clustering (or aggregation) of cars occurs in our model. The mean distance ⟨l⟩ between cars scales as ⟨l⟩≈t0.37±0.02 where t is time. Similarly, the mean cluster size ⟨s⟩ of cars scales as ⟨s⟩≈t0.37±0.02. It is shown that the cumulative cluster-size distribution Ns is not a power-law type but an exponential function Ns≈⟨s−1 e−1.72s⁄⟨s.
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  • Minoru Fukui, Yoshihiro Ishibashi
    1993 Volume 62 Issue 11 Pages 3841-3844
    Published: November 15, 1993
    Released on J-STAGE: May 29, 2007
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    Traffic flow is simulated in a three-state cellular automaton model. In a two-dimensional cell without a crashed car, the ensemble average of the velocity of the cars is enhanced by the self-organization in the low-density phase of cars. In the high-density phase above p=0.5 of car density, the velocity is decreased and the system then degenerates into a global jamming phase in which all cars are stopped. A crashed car provides the seed of a jamming cluster, which grows into a global traffic jam even in the low-density phase. The growth of the jamming cluster is studied, and the time dependence of the number of jamming cars and the scaling law for the cell sizes are discussed.
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  • Taro Nagao, Miki Wadati
    1993 Volume 62 Issue 11 Pages 3845-3856
    Published: November 15, 1993
    Released on J-STAGE: June 01, 2007
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    Local eigenvalue correlations are exactly evaluated at the edge region for random matrix ensembles related to orthogonal polynomials on a finite real interval. We define a determinant of a quaternion matrix and utilize it for the evaluation. It is shown that there is an exact equivalence between the local correlations for Jacobi and Laguerre ensembles of random matrices.
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  • Kazuhiro Hikami, Miki Wadati
    1993 Volume 62 Issue 11 Pages 3857-3863
    Published: November 15, 1993
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    It is proved that the classical Calogero model is a realization of the U(1) current algebra. The relations with the hermitian one-matrix model are explicitly shown. In particular, the coupling constants in the potential of the matrix model are identified as the “time” variables of the classical Calogero model, which are conjugate to the conserved quantities. Furthermore, the Calogero model is related to the integrable nonlinear evolution equations.
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  • Shintaro Mori, Miki Wadati
    1993 Volume 62 Issue 11 Pages 3864-3873
    Published: November 15, 1993
    Released on J-STAGE: June 01, 2007
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    In the large limit of the embedding space dimension d, D-dimensinal tethered membranes are studied. Quenched disorders in the internal preferred metric and the spontaneous curvature, and long range repulsive interactions which fall off with distance r like 1⁄rγ are assumed. The flat phase is unstable due to the disorder of the metric and the spin-glass phase takes over as in the phantom randomly polymerized membrane case. A complete phase diagram in the (γ, D) plane is obtained. The crumpled phase of the membranes is not affected by the randomnesses and the existence region remains the same. The exact exponent for the radius of gyration in the spin-glass phase is given. From a comparison with the crumpling transition in the self-avoiding tethered membrane, we propose a conjecture that the wrinkling transition dose not exist in the self-avoiding randomly polymerized membrane.
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  • Katsuhisa Koura
    1993 Volume 62 Issue 11 Pages 3874-3880
    Published: November 15, 1993
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    The statistical inelastic cross-section [SICS(D)] model for molecules with discrete rotational energy is used for the Monte Carlo simulation of rarefied nitrogen gases contained between two parallel plates at a large temperature difference with the null-collision direct-simulation Monte Carlo method. The density distribution is compared with the experimental data and fair agreement is obtained for the fully diffuse reflection plates. The rotational distribution near the cold plate indicates the bimodal form represented approximately by the merging of two Boltzmann distributions at the cold and hot plate temperatures.
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  • Hidekazu Tsuji, Masayuki Oikawa
    1993 Volume 62 Issue 11 Pages 3881-3892
    Published: November 15, 1993
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    Two-dimensional interaction of internal solitary waves is studied for a two-layer fluid with a thickness ratio close to a certain critical one depending on the density ratio. It is described by a Modified Kadomtsev-Petviashvili (MKP) equation, provided the propagation directions of the waves are close to each other. The MKP equation is investigated numerically and it is found that the interaction almost satisfying the condition of soliton resonance occurs when the wave amplitudes are small. The interaction is qualitatively similar to the soliton resonance in the Kadomtsev-Petviashvili (KP) equation except that a deformation of the newly generated waves and a radiation can be seen.
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  • S. K. Ghosh
    1993 Volume 62 Issue 11 Pages 3893-3903
    Published: November 15, 1993
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    Unsteady hydromagnetic flow of a viscous incompressible electrically conducting fluid confined between rotating parallel plate non-conducting channel flow under the influence of an oscillating pressure gradient permeated by anuniform transverse magnetic field of which induced magnetic field is taken into account, is studied. The solution in dimensionless form contains four flow parameters viz., αm, E, Pm and ω are, respectively, the magnetic interaction parameter, Ekman number, magnetic Prandtl number and frequency parameter. Asymptotic behaviour of the solution is analysed for large ω. The numerical results of velocity, induced magnetic field and shear stress are shown graphically and the mean sectional velocities are presented numerically.
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  • Taro Matsumoto, Yuji Nakamura, Masahiro Wakatani
    1993 Volume 62 Issue 11 Pages 3904-3918
    Published: November 15, 1993
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    Averaged flux surfaces with respect to the toroidal angle in l=2 heliotron/torsatrons are deformed in D-shape or inverse D-shape by the hexapole field. D-shape deformation of vacuum flux surfaces enhances magnetic well or reduces magnetic hill in Heliotron-E and Large Helical Device (LHD) configuration. However, complete elimination of the magnetic hill region is not obtained by the D-shape deformation without substantial reduction of plasma radius. The inverse D-shape deformation degrades MHD stability against ideal interchange modes in the central region of both devices for fairly peaked pressure profiles. In the LHD configuration, a broad pressure profile proportional to (1−ψ2)2 degrades the MHD stability and the hexapole effect is almost irrelevant, where ψ is a poloidal flux function; however, second stability appears against both the local and non-local interchange modes.
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  • Michio Matsumoto
    1993 Volume 62 Issue 11 Pages 3919-3928
    Published: November 15, 1993
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    A positive column with negative ions in a uniform longitudinal magnetic field B is analytically proved unstable in two modes of low frequency waves, i.e., the modes of ionization wave and of helical wave. The former mode is excited in B<Bc and the latter in BBc, Bc being the critical field above which the plasma is helically unstable. Effects of the negative ions and of the field B on those low frequency waves are discussed on the basis of a same ratio approximation for charged particle density perturbations.
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  • Hirotake Shigematsu, Hironobu Kasano, Hiroyuki Mashiyama
    1993 Volume 62 Issue 11 Pages 3929-3935
    Published: November 15, 1993
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    The crystal structures of phases I, III and IV of (NH4)2ZnBr4 were determined at 175°C, 25°C and −130°C, respectively, by single-crystal X-ray diffractometry. The space groups are Pmcn (phase I), P21c11 (phase III) and P21cn (phase IV). In the disordered phase I, each ZnBr4 tetrahedron occupies two sites with equal probability to satisfy the mirror symmetry. This disorderness disappears in phases III and IV, and the primary structural change is described that the ZnBr4 tetrahedra rotate about the axis parallel to the c-axis accompanying with a translation along the a-axis. In an intermediate temperature range between phases III and IV, additional reflections that do not belong to the phase III nor IV are sometimes observed in a few samples. This indicates that a metastable state which is similar to the sevenfold phase of (NH4)2ZnCl4 can appear there.
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  • Tsuguhiro Abe, Masaharu Tokunaga
    1993 Volume 62 Issue 11 Pages 3936-3942
    Published: November 15, 1993
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    The lattice structure possible in the low-temperature phase of the Ih-XI transition in ice is studied from a statistical mechanical viewpoint. The entropy is calculated as a function of order parameters to clarify the role of the ice constraint within the Bragg-Williams approximation. The internal energy is introduced only in the quadratic form of order parameters. The order parameter is proved to show the jump between 1 and 0 at the Ih(P63mmc)-Cmc21 transition in analytical manner. The Ih-P63mc transition was recently proposed on the basis of experimental results of neutron diffraction, but is proved to be of second order contrary to the experimental results indicating the first order transition accompanied with the anomalously large thermal relaxation time.
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  • Takeo Takagi, Mamoru Mekata
    1993 Volume 62 Issue 11 Pages 3943-3953
    Published: November 15, 1993
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    The magnetic ordering of classical Ising spins on the Kagomé lattice were studied taking into account the second neighbor interaction in addition to the antiferromagnetic nearest neighbor interaction by means of Monte Carlo simulations and mean field approximation. In the ferromagnetic second neighbor interaction case, the phase transition from the ferrimagnetic ordered ground state to a partially disordered state characterized by quasi-long range Kosterlitz-Thouless type order was found. The antiferromagnetic second neighbor interaction gives rise to no stable long range order at finite temperatures and the ground state is characterized by a quasi-long range order with intensive fluctuations.
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  • Norikazu Ishimura, Takao Yamamoto
    1993 Volume 62 Issue 11 Pages 3954-3964
    Published: November 15, 1993
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    A model which simulates a system of magnetic-atom chain adsorbed on a crystal surface is proposed. The present model differs from the conventional Frenkel-Kontorova model at the point that each atom in the adlayer chain is magnetic and the strength of the exchange interaction between the nearest neighbor adatoms varies with the distance between the two atoms. The chain of the adsorbed atoms is modulated by an external magnetic field. The properties of the system at zero temperature and low temperatures are discussed by the effective potential method.
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  • Hirohiko Adachi
    1993 Volume 62 Issue 11 Pages 3965-3973
    Published: November 15, 1993
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    The discrete variational (DV) Xα cluster method has been used for investigations of the electronic state and bonding nature of alkali halide crystals. The bonding in these compounds which is considered to be typically ionic, contains covalent character to a certain extent. It is found that the covalency increases when the atomic number of halogen increases and that of alkali decreases. The ionic radius determined from the electronic charge density calculated deviates from Pauling’s value, according to the extent of covalency.
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  • Mitsuharu Nagasawa, Takashi Sambongi, Kazushige Nomura, Hiroyuki Anzai
    1993 Volume 62 Issue 11 Pages 3974-3978
    Published: November 15, 1993
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    In the spin density wave (SDW) phase of (TMTSF)2AsF6 and (TMTSF)2PF6, we measured the metal-insulator transition temperature TMI and the activation energy EA in the SDW insulating phase under pressure. The ratio 2EAkBTMI near the critical pressure ∼10.5 kbar, above which the SDW phase does not exist, is examined and compared with the mean-field theory developed by Yamaji. We conclude that TMI does not correspond to the normal-SDW transition temperature TSDW but is lower than TSDW. Non-linear conduction with finite threshold was observed above TMI.
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  • Tomi Ohtsuki, Keith Slevin, Yoshiyuki Ono
    1993 Volume 62 Issue 11 Pages 3979-3987
    Published: November 15, 1993
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    The conductance of a two-dimensional system subject to a random magnetic field is calculated within the Landauer-Büttiker formalism. Although there is no potential disorder the random fluctuating magnetic field introduces a random vector potential. Electrons in bulk states are found to be strongly scattered by the fluctuating field. In contrast, edge states are found to be quite stable even if the fluctuation of the field is of the order of a uniform background field. In a fully random field, the U(1) model, clear universal conductance fluctuations (UCF) are observed. The magnitude of the fluctuations is compared with that in the time reversal symmetric Z2 model.
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  • Arisato Kawabata
    1993 Volume 62 Issue 11 Pages 3988-4000
    Published: November 15, 1993
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    Boundary roughness scattering in quantum wires is investigated. A new formulation to construct an effective potential beyond the perturbation theory and the adiabatic approximation is proposed. The theory of scattering in quasi-one dimensional systems which was proposed by the author to account for the higher order perturbation is re-investigated and is applied to a single-subband wire in the presence of screening by conduction electrons. Effects of screening in a multi-subband wire is also investigated and it is shown, at least for two-subband wires, that at low temperatures the currents carried by each subband become equal because of the peculiarity of the screening in quasi one-dimensional systems.
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  • Mahito Kohmoto
    1993 Volume 62 Issue 11 Pages 4001-4008
    Published: November 15, 1993
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    Networks of thin wires in a magnetic field (or without a magnetic field) are related to tight-binding models on the same nets. The Hall conductance of a two-dimensional regular or random network is quantized when the Fermi energy is in a gap of extended states. It provides the possibility that the novel quantized Hall effect in two-dimensional periodic systems predicted by Thouless et al. [Phys. Rev. Lett. 49 (1982) 405] is observed in an artificially constructed network.
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  • Hiroshi Harashina, Shin-ichi Shamoto, Takanori Kiyokura, Masatoshi Sat ...
    1993 Volume 62 Issue 11 Pages 4009-4015
    Published: November 15, 1993
    Released on J-STAGE: May 29, 2007
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    Neutron scattering measurements of magnetic excitations in YBa2Cu2.9Zn0.1O6.75 (Tc≤10 K) have been performed. In contrast to the corresponding pure sample with the same oxygen number (Tc\simeq66 K) where no peak of the antiferromagnetic correlation was detected for excitation energies below 15 meV, we have observed clear scattering contribution in the same energy range at all temperatures studied. A detailed study of χ″(ω) at (π, π) in this Zn-substituted sample suggests 1) an existence of the gap-like structure at high temperatures (100 K<T<200 K) and 2) the enhancement of the spectral weight at low energies along with the loss of the itinerant nature of the electrons at low temperatures (T<50 K).
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  • Masafumi Kyogaku, Yoshio Kitaoka, Kunisuke Asayama, Christoph Geibel, ...
    1993 Volume 62 Issue 11 Pages 4016-4030
    Published: November 15, 1993
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    Both magnetic and superconducting characteristics of the new heavy fermion superconductors (HFS), UNi2Al3 and UPd2Al3 have been investigated extensively by means of 27Al NMR and NQR. Systematic studies of the nuclear-spin-lattice relaxation time T1, the Knight shift and the spectrum of 27Al have revealed different types of magnetic fluctuations and spin structure between these two compounds. UNi2Al3 shows a band-type itinerant antiferromagnetic behavior, while UPd2Al3 belongs to a heavy fermion antiferromagnet with an ordinary size of U-derived moment. In the superconducting state, the relaxation behavior in UPd2Al3 is similar to those observed in the other HFS reported so far, providing an evidence for an unconventional anisotropic superconductivity with line of gap zeros on the Fermi surface as well. Knight shift has been found to decrease considerably below Tc, showing that the pseudo spin is well defined, not affected by the impurity scattering.
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  • Kazuki Kanki, Kosaku Yamada
    1993 Volume 62 Issue 11 Pages 4031-4043
    Published: November 15, 1993
    Released on J-STAGE: June 01, 2007
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    In heavy electron systems, because of the strong renormalization of the electronic states by electron-electron interaction, the electron-phonon coupling is much reduced. As a result vertex corrections by the electron-phonon interaction is negligible for the electron-phonon interaction vertex with frequency of phonon proper for quasiparticle pairing, although the usual Migdal’s theorem no longer holds as a result of the reduction of the Fermi energy. By solving the Eliashberg equation and taking account of the Grüneisen parameter, we show that it is difficult to attribute the origin of the attractive interaction responsible for superconductivity to the electron-phonon interaction. On the other hand, the Coulomb interaction between quasiparticles is shown to maintain the coupling constant of the same order as that before the renormalization, and can be considered as the possible origin of the anisotropic superconductivity.
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  • Susumu Matsuo, Hiroshi Nakano, Tsutomu Ishimasa, Masahiro Mori
    1993 Volume 62 Issue 11 Pages 4044-4052
    Published: November 15, 1993
    Released on J-STAGE: May 29, 2007
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    Magnetic properties were studied for single-grained Al68Pd23Mn9 icosahedral quasicrystals which had high degree of structural perfections. An anisotropy associated with the directional order in the icosahedral phase was found for the first time in the nonlinear region of the magnetization-vs-magnetic-field curve of the single-grained quasicrystal along 5-, 3-, and 2-fold axes below 40 K. No anisotropy was found in the linear region, which is consistent with a symmetry consideration based on the icosahedral symmetry. The magnetic susceptibility obeyed a Curie-Weiss law with a Curie-Weiss temperature −0.81 K which suggests a weak antiferromagnetic coupling between magnetic moments.
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  • Hidekazu Tanaka, Toshiaki Hasegawa, Kazukiyo Nagata
    1993 Volume 62 Issue 11 Pages 4053-4065
    Published: November 15, 1993
    Released on J-STAGE: May 29, 2007
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    The Rb1−xKxNiCl3 system is a mixture of S=1 Heisenberg antiferromagnets on deformed triangular lattice with the easy-axis and easy-plane types of anisotropy. The magnetic phase transitions in the present system were investigated by susceptibility and torque measurements. A phase diagram for temperature vs x was determined. With increasing x the anisotropy changes from the easy-axis type to the easy-plane one at xc=0.38. For x<xc one phase transition occurs, while for xc<x<0.8 two transitions take place. The intermediate phase appears at xc where the anisotropy changes its sign, and the temperature range of the intermediate phase is enhanced on increasing x. The magnetic properties for xc<x<0.8 are similar to those of RbVBr3 which has a deformed triangular lattice in the c-plane. The successive transition was not observed in the vicinity of x=1 where the symmetry of the crystal lattice is lower than that for x<0.8.
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  • Allan E. Jacobs, Tetsuro Nikuni, Hiroyuki Shiba
    1993 Volume 62 Issue 11 Pages 4066-4080
    Published: November 15, 1993
    Released on J-STAGE: May 29, 2007
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    At zero field CsCuCl3 is known to form a helical spin structure along the c-axis and the 120° structure in the c-plane. This paper discusses theoretically the effect of a magnetic field applied perpendicular to the c-axis, which breaks the axial symmetry. First the classical ground state is studied. The transverse magnetic field deforms the helical spin structure and causes a continuous phase transition from the helical (i.e. incommensurate) spin structure to a commensurate state, as the field increases. Detailed studies are made of the helix pitch and of the nature of the incommensurate spin structure as functions of the field. The commensurate state has a nontrivial degeneracy, which is lifted by quantum (and thermal) fluctuations. Therefore the 1⁄S expansion is applied to determine the spin structure of the commensurate state. From these studies possible spin structures are suggested for each region of field strength.
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  • Masahiro Matsumura, Seiya Nishiyama, Yuji Iwamoto, Hideki Yamagata
    1993 Volume 62 Issue 11 Pages 4081-4092
    Published: November 15, 1993
    Released on J-STAGE: May 29, 2007
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    The Cu-NMR spectrum for Cu(2) site was measured from 1.5 K to 200 K in the quasi-two dimensional (2D) bilayer antiferromagnet, YBa2Cu3O6.1. The nuclear Zeeman and quadrupole frequencies, νL and νQ were deduced from the spectrum. The decrease of the sublattice magnetization with increasing temperature was evaluated from the values νL as (νL(0)−νL(T))⁄νL(0) assuming no temperature dependence of the hyperfine coupling constant. The evaluated sublattice magnetization shows the almost linear temperature dependence at least above 25 K in log ((νL(0)−νL(T))⁄νL(0)) vs. log T plot. This temperature dependence of the sublattice magnetization is well explained quantitatively within a factor of two by the spin wave model in the quasi-2D antiferromagnet using the exchange coupling parameters reported previously by neutron scattering experiments.
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  • Mitsumasa Ishiwata
    1993 Volume 62 Issue 11 Pages 4093-4103
    Published: November 15, 1993
    Released on J-STAGE: June 01, 2007
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    The recovery after selective inversion of a 13C-line in a coupled 13C–1H spin system in 13C-enriched formic acid is observed under the just-resonance irradiation to one of the 1H-doublet lines. The continuous rf is not too strong to result in any appreciable splitting of the observed line. It is found that only the recovery of a line which is progressively connected to the stirred one can considerably be accelerated by the rf when it partially, not completely, saturate absorption of the stirred line. The acceleration is due to both of coherent and incoherent effects of the rf, while the latter one considerably retards the recovery for regressively-connected combinations of the observed and stirred lines. A detailed account of these phenomena based on a relaxation-mode analysis of the recovery process is given.
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  • Yositaka Onodera
    1993 Volume 62 Issue 11 Pages 4104-4107
    Published: November 15, 1993
    Released on J-STAGE: June 01, 2007
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    Although Debye’s relaxation model has been extensively used in analyzing experimental data of dielectric dispersion and absorption, the model has a fault to violate the sum rule for dielectric function. A simple and tractable modification to Debye’s model is proposed which is free from the above-mentioned fault. The resulting Cole-Cole diagram is shown to deviate from an exact circle.
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  • Takashi Fujikawa, Takafumi Miyanaga
    1993 Volume 62 Issue 11 Pages 4108-4122
    Published: November 15, 1993
    Released on J-STAGE: June 01, 2007
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    Temperature dependence of EXAFS, EELFS and ARXPS is discussed in the framework of plane wave approximation, where we take the cubic and quartic anharmonicity into account. First we apply cumulant expansion whose expanded terms are written in terms of corresponding lower order moments and cumulants. Secondly we apply temperature Green’s function technique systematically to calculate these moments for perfect crystals with translational symmetry. We furthermore discuss high and low temperature behavior of these cumulants, and also describe real space representation of them in comparison with widely used classical expression. This real space representation needs no translation symmetry, and we discuss the applicability of the classical local space integral formula.
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  • Kouichi Ichikawa, Takashi Umehara, Osamu Aita, Kenjiro Tsutsumi
    1993 Volume 62 Issue 11 Pages 4123-4128
    Published: November 15, 1993
    Released on J-STAGE: May 29, 2007
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    The rare-earth N4,5 emission spectra of PrB6 and NdB6 were measured to investigate the 4f states. These spectra show some emission peaks above and below the one-electron 4d threshold. The emission spectra are compared with existing results of absorption and resonant photoemission. Comparison shows that the emission spectra are composed of two types of 4f→4d emission processes, 4d94fn→4d104fn−1+hν and 4d94fn+1→4d104fn+hν′, where n is the number of 4f electrons in the ground state. The intensity of the 4f→4d emission is estimated for light rare-earth hexaborides. This result suggests that the intensity of the 4f→4d emission is weaker than the 5p→4d emission.
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  • Tsuneaki Miyahara, Takaaki Hanyu, Hiroyoshi Ishii, Tsutomu Mitsuishi, ...
    1993 Volume 62 Issue 11 Pages 4129-4136
    Published: November 15, 1993
    Released on J-STAGE: May 29, 2007
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    The valence and Ce 4d photoemission spectra of CeRu2 were measured in the 3d-4f resonance region without being complicated by strong Auger lines. Because of the strong Coster-Kronig decay channel the resonance due to 3d3⁄2-4f excitation was found to be much weaker than that for 3d5⁄2-4f excitation both for the valence and the 4d spectra. The spectral shape of the valence and the 4d electrons were changed in the two resonance regions, and especially the changes in the 4d spectra were drastic near the 3d3⁄2-4f excitation region. A tentative interpretation of the drastic change is given in terms of an energy exchange between two continuum states following the Coster-Kronig decay.
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  • Norimichi Kojima, K\={o}zo Ito, Iwao Mogi, Masayasu Takeda, Giyuu Kido ...
    1993 Volume 62 Issue 11 Pages 4137-4145
    Published: November 15, 1993
    Released on J-STAGE: June 01, 2007
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    We have investigated exciton-magnon absorption spectra in VX2 (X=Cl, Br and I) and LiCrO2 known as two-dimensional Heisenberg triangular lattice antiferromagnets (2DH TAL–AF) in order to study the effect of the peculiar spin frustration on the magnetic elementary excitations. In VX2 (X=Cl and Br) and LiCrO2, the temperature dependence of the line width of the exciton-magnon absorption resembles closely that of the density of the characteristic point defects known as Z2-vortex in 2DH TAL–AF. Thus the line width of the exciton magnon absorption in 2DH TAL–AF exhibits Z2-vortex induced broadening. We also reported the magnetic Raman scattering in VCl2 and VI2.
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  • Tetsu Mieno
    1993 Volume 62 Issue 11 Pages 4146-4147
    Published: November 15, 1993
    Released on J-STAGE: May 29, 2007
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