-
Jirka Hlinka, Yoshihiro Ishibashi, Tomoyuki Nagaya
Subject area: Equations of state, phase equilibria, and phase transitions.
1998 Volume 67 Issue 12 Pages
3999-4001
Published: December 01, 1998
Released on J-STAGE: October 01, 1999
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Coarsening of a domain pattern during the cooling process in type-II incommensurate ferroelectrics like NaNO
2 or thiourea is investigated in the framework of two-dimensional discrete lattice model derived from the Ishibashi-Shiba potential. The cooling process is simulated by gradual change of the parameters of potential with time.It has turned out that the resultant domain patterns differ depending on the cooling rate.The present lattice model can satisfactorily reproduce the formation of lamellar and amorphous domain patterns actually observed in NaNO
2.
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Masahiko Hatatani, Osamu Narikiyo, Kazumasa Miyake
Subject area: Electron states in condensed matter.
1998 Volume 67 Issue 12 Pages
4002-4005
Published: December 01, 1998
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The uniform spin susceptibility χ around the quantum critical point is discussed on the basis of the mode-mode coupling theory of the antiferromagnetic (AF) spin fluctuations. The temperature dependence of χ around the quantum critical point reflects the magnetic-field dependence of the free energy due to that of the spin fluctuations. The results are χ ∝ 1-β
2t
1/4 for the conventional class of AF fluctuations with the dynamical exponent z=2, and χ ∝ 1-β
3t
1/3 for a new class of AF fluctuations with z=3, where t is the reduced temperature and β
2 and β
3 are numerical constants. For Ce
7Ni
3, the behavior of χ around the quantum critical point is possibly explaned by this theory with the conventional class of AF fluctuations with z=2. The latter type of AF fluctuations with z=3 is possible when the system contains even number of magnetic ions in the unit cell such as CeCu
6-xAu
x (x=0.1), because the AF ordering vector can coincide with one of the reciprocal lattice vectors.
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Marcus Metzler
Subject area: Electron states in condensed matter.
1998 Volume 67 Issue 12 Pages
4006-4009
Published: December 01, 1998
Released on J-STAGE: October 01, 1999
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We investigate the spectral statistics of a network model for a three-dimensional layered quantum Hall system numerically. The scaling of the quantity J
0=½‹ s
2› is used to determine the critical exponent ν for several interlayer coupling strengths. Furthermore, we determine the level spacing distribution P(s) as well as the spectral compressibility χ at criticality. We show that the tail of P(s) decays as exp(-κ s) with κ=1/(2χ) and also numerically verify the equation χ=(d-D_2)/(2d), where D_2 is the correlation dimension and d=3 the spatial dimension.
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Satoshi Nishimoto, Yukinori Ohta
Subject area: Electron states in condensed matter.
1998 Volume 67 Issue 12 Pages
4010-4013
Published: December 01, 1998
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An exact-diagonalization technique on small clusters is used to calculate the dynamical density correlation functions of the dimerized t-J chain and coupled anisotropic t-J ladders (trellis lattice) at quarter-filling, i.e., the systems regarded as a network of pairs (dimers or rungs) of sites coupled weakly via the hopping and exchange interactions. We thereby demonstrate that the intersite Coulomb repulsions between the pairs induce a low-energy collective mode in the charge excitations of the systems where the internal charge degrees of freedom of the pairs play an essential role. Implications to the electronic states of NaV
2O
5, i.e., fluctuations of the valence state of V ions and phase transition as a charge ordering, are discussed.
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Yasuhiro Asano
Subject area: Electron states in condensed matter.
1998 Volume 67 Issue 12 Pages
4014-4017
Published: December 01, 1998
Released on J-STAGE: October 01, 1999
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We studied the electronic structure and the electron transport in vertically coupled double quantum dots as a function of the number of electrons and strength of the magnetic field applied in the direction perpendicular to the electric current. In weakly coupled double quantum dots, the electron correlation leads to the spin blockade in the Coulomb oscillations of the conductance. To date, however, it has been difficult to observe the spin blockade clearly since the temperature is not sufficiently low. We propose an experimental method to confirm the electron correlation effects even in the present temperature regime.
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Kazuhiko Hasegawa, Hideaki Kasai, Wilson Agerico Diño, Ayao Oki ...
Subject area: Electronic structure and electrical properties of surfaces, interfaces and thin films.
1998 Volume 67 Issue 12 Pages
4018-4021
Published: December 01, 1998
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We propose a simple model to describe the dynamics of STM-induced desorption of a single CO molecule from Cu(111). In the model, a single electron initially occupies the CO 2π
*-orbital. An excitation of the CO-Cu stretching vibration then occurs when this electron subsequently transfers/tunnels from the CO 2π
*-orbital to the metal substrate. When the excitation of the CO-Cu stretching vibration exceeds some predesorption level in a truncated harmonic oscillator well, CO is desorbed from Cu(111). The results of our model calculation for the desorption probability agree quite well with recent experimental results.
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Makoto Isoda, Shigeyoshi Mori
Subject area: Magnetic properties and materials.
1998 Volume 67 Issue 12 Pages
4022-4025
Published: December 01, 1998
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The valence-bond crystal is proposed as a ground state of spin-1/2 Heisenberg antiferromagnet on 3-dimensional fully frustrated pyrochlore by the bond-operator theory. This crystal, formed as a set of RVB-like tetrahedral singlet states, has lower energy than the state consisting of two dimers in a tetrahedron. The spectra of triplet excitation have a finite gap and a symmetry lower than that of the lattice. The comparison with Y(Sc)Mn
2 is discussed.
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Setsuo Mitsuda, Noriaki Kasahara, Takahiro Uno, Motoshi Mase
Subject area: Magnetic properties and materials.
1998 Volume 67 Issue 12 Pages
4026-4029
Published: December 01, 1998
Released on J-STAGE: October 01, 1999
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We reinvestigated successive magnetic phase transitions (T
N1-- 14.0K, T
N2-- 10.5K) in a frustrated triangular lattice antiferromagnet (TLA) CuFeO
2 by neutron diffraction measurements using single crystals. The magnetic structure of the intermediate-temperature phase between T
N1 and T
N2 is found to be a quasi-long range ordered sinusoidally amplitude-modulated structure with a temperature dependent propagation wave vector (q q 0). These features of successive phase transitions are well explained by reinvestigated Monte-Carlo simulation of a 2D Ising TLA with competing exchange interactions up to 3rd neighbors, in spite of the Heisenberg spin character of orbital singlet Fe
3+ magnetic ions.
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Sindhunivas G. Bindu, Valakkattil C. Kuriakose
Subject area: Mathematical methods in physics.
1998 Volume 67 Issue 12 Pages
4031-4036
Published: December 01, 1998
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Electromagnetic wave propagation through cold collision free plasma is studied using the nonlinear reductive perturbation method. We have studied the propagation of electromagnetic wave through plasma in (1+1) dimensions and in (2+1) dimensions. It is found that to the lowest order of perturbation the system of equationscan be reduced to modified Korteweg-deVries equation in (1+1) dimensions and to modified Kadomtsev-Petviashvili equation in (2+1) dimensions.
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Kazuhiro Hikami, Yasushi Komori
Subject area: Mathematical methods in physics.
1998 Volume 67 Issue 12 Pages
4037-4044
Published: December 01, 1998
Released on J-STAGE: October 01, 1999
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We study the elliptic Ruijsenaars model of type-BC, which is adifference analogue of the BC-type Calogero--Sutherland--Moser modelwith an elliptic pairwise potential.In the trigonometric limit, the difference operator of this model reduces to the Macdonald--Koornwinder operatorby a gauge-transformation.We show that our difference operatoracts on a finite-dimensional space of functions in a special case of thecoupling constant.
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Ruguang Zhou, Wen–Xiu Ma
Subject area: Mathematical methods in physics.
1998 Volume 67 Issue 12 Pages
4045-4050
Published: December 01, 1998
Released on J-STAGE: October 01, 1999
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A new finite-dimensional classical integrable system and a new quantum integrable system are generated from a spectral problem for the MKdV hierarchy through the nonlinearization technique of Lax systems. Our classical integrable system is an example of Gaudin magnet with boundary and relates to the finite band solutions of the MKdV hierarchy. Its Lax representation and r-matrix is given, and its separation of variables is performed. Based on a direct link between r-matrix formulas for classical systems and quantum problems, a quantum integrable system with separated variables is presented.
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Masayoshi Tajiri, Takahito Arai, Yosuke Watanabe
Subject area: Mathematical methods in physics.
1998 Volume 67 Issue 12 Pages
4051-4057
Published: December 01, 1998
Released on J-STAGE: October 01, 1999
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The exact solutions to the Davey-Stewartson I equationare analyzed to study the nature of the interactions betweeny-periodic soliton and line soliton and between y-periodic solitonand algebraic soliton.The interactions are classified into several types according tothe phase shifts due to collisions.There are two types of singular interactions:one is the resonant interaction where two solitons interactso as to make one soliton and the other is the extremely long-range interactionwhere two solitons interchange each other infinitely apart.Detail behaviors of interactions are illustrated graphically.
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Takashi Kanamaru, Takehiko Horita, Yasunori Okabe
Subject area: Statistical physics and thermodynamics.
1998 Volume 67 Issue 12 Pages
4058-4063
Published: December 01, 1998
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Stochastic resonance in a coupled Hodgkin-Huxley equation is investigated.The dependence of signal to noise ratio on the frequencies of the periodic input signals is examined by numerical experiments.Two or three Hodgkin-Huxley equations are coupled with a propagationaltime delay to compose a network.For a network with two elements, an enhancement of the stochastic resonancefor the periodic input signals with particular frequencies is found.It is also found that a network with three elements is capable of distinguishing periodic input signals by those frequencies.
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Takayasu Fukuhara, Hiizu Nakanishi
Subject area: Mechanics, elasticity, and rheology.
1998 Volume 67 Issue 12 Pages
4064-4067
Published: December 01, 1998
Released on J-STAGE: October 01, 1999
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Dynamical stability of the crack front line that propagates betweentwo plates is studied numerically using the simple two-dimensionalmass-spring model. It is demonstrated that the straightfront line is unstable for low speed while it becomes stable for high speed.For the uniform model, the roughness exponent in the slower speedregion is fairly constant around 0.4 and there seems to be arough-smooth transition at a certain speed.For the inhomogeneous case with quenched randomness, the transition is gradual.
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Makoto Iima, Sadayoshi Toh
Subject area: Fluid dynamics.
1998 Volume 67 Issue 12 Pages
4068-4073
Published: December 01, 1998
Released on J-STAGE: October 01, 1999
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In the analysis of orthonormal wavelet, standard definitions of physical quantities such as energy in wavelet space are not free from spatial oscillation intrinsic to wavelet base function, i.e., phase in contrast to the Fourier analysis.Moreover the energy summed over a scale is not translationally invariant.To remove the phase, we propose a kind of spatial averaging in terms of extended continuous wavelet.The translational invariance of energy is recovered by means of this averaging method. This method is also applied to the transfer functions which were defined in terms of orthonormal wavelet in the previous paper [Phys. Rev. E 52 (1995) 6189].
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Jae–Tack Jeong
Subject area: Fluid dynamics.
1998 Volume 67 Issue 12 Pages
4074-4079
Published: December 01, 1998
Released on J-STAGE: October 01, 1999
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Two-dimensional slow viscous flow through a slit in a vertical plate on a plane wall is investigated based on the Stokes approximation. The width and the distance of the slit from the plane wall are taken arbitrary. The plane wall is at rest and the flow is generated by a pressure difference between two sides of the plate at infinity. A formal expression for the flow is obtained by solving a three-part Wiener-Hopf equation. By evaluating the formal expression, streamline patterns for typical cases are drawn. Flowrate through the slit and velocity profile on the slit are determined. The pressure distributions on the boundaries are shown and the force and moment exerted on the inner plate are also calculated.
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Sanae–I. Itoh, Shinichiro Toda, Masatoshi Yagi, Kimitaka Itoh, A ...
Subject area: Kinetic and transport theory of fluids; physical properties of gases.
1998 Volume 67 Issue 12 Pages
4080-4083
Published: December 01, 1998
Released on J-STAGE: October 01, 1999
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Statistical property of an excitation of plasma transitionis analyzed, which takes place in a strongly turbulent state. Transition characteristics which have been studied in a deterministic picture are re-examined.Model equations of transition, with a hysteresis naturein flux-gradient relation in the presence of strong self-noise, are solved and the dynamics of plasma gradient and turbulent-driven flux is studied. The excitation probability is shown to be fairlylarge well below the conventional critical condition. Probability distribution function, as a function of the gradient, for an onset of the transition is obtained both for power law noise.
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Yasuhiko Sentoku, Kunioki Mima, Yasuaki Kishimoto, Mitsuru Honda
Subject area: The physics of plasmas and electric discharges.
1998 Volume 67 Issue 12 Pages
4084-4088
Published: December 01, 1998
Released on J-STAGE: October 01, 1999
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Relativistic binary collision effects on the intense laser plasmainteractions are investigated by introducing the Monte Carlo Coulomb modelinto a particle simulation code.Our collision model is fully relativistic, where the collision frequency iscalculated in the frame work of relativistic electro-dynamics.By the particle simulation, the following two phenomena which are importantin laser plasmas are investigated.The first one is for the electron heat transport in a steep temperaturegradient and the second is for the electron energy distribution function ofplasmas heated by a relativistic intensity laser irradiation.The results of the simulations are compared with the results of numericalanalysis of the Fokker-Planck equation.
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Katsumi Ida, Yukitoshi Miura, Kimitaka Itoh, Sanae–I. Itoh, Tosh ...
Subject area: The physics of plasmas and electric discharges.
1998 Volume 67 Issue 12 Pages
4089-4097
Published: December 01, 1998
Released on J-STAGE: October 01, 1999
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A nondiffusive term in the toroidal-momentum-transport equation is evaluated by the analysis of the transport of toroidal rotation in the transient phase, where the direction of neutral beam injection is changed from parallel to the plasma current to antiparallel. The ratio of nondiffusive viscosity coefficient to diffusive viscosity coefficient is evaluated to be 0.1 to 0.3, which increases as the plasma current is decreased. Nondiffusive momentum transport is found to be in proportion to {\
abla}T
i.
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Rosangela B. Pereira, Antonio L. A. Fonseca, Oliveira A. C. Nunes
Subject area: The physics of plasmas and electric discharges.
1998 Volume 67 Issue 12 Pages
4098-4103
Published: December 01, 1998
Released on J-STAGE: October 01, 1999
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The plasmon instability in a laboratory produced plasma in the presence of four external fields, namely two laser fields, one strong magnetic field and one static electric field, is discussed. The method of unitary transformations is used to transform the problem of electron motion under the four external fields to that of an electron in the presence only of crossed electric and magnetic fields. A kinetic equation for the plasmon population is derived from which the damping (amplification) rate is calculated. We found that the joint action of the four fields results in a relatively larger amplification rate for some values of the static electric field in contrast to the case where no electric field is present. It was also found that the plasmon growth rate favors plasmon wave vectors in an extremely narrow band i.e., the plasmon instability in four external fields is a very selective mechanism for plasmon excitation.
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Tomohiro Ikeda, Masaki Takata, Makoto Sakata, Janusz Waliszewski, Ludw ...
Subject area: Structure of liquids and solids; crystallography.
1998 Volume 67 Issue 12 Pages
4104-4109
Published: December 01, 1998
Released on J-STAGE: October 01, 1999
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The electron density distribution of wurtzite-type gallium nitride (w-GaN) was obtained by the Maximum Entropy Method (MEM) using the Synchrotron Radiation powder data. Contribution of the very minor zinc blende-type phase (z-GaN) to the observed powder data was eliminated by the modified Rietveld method. In the obtained MEM electron density distribution map, there are two kinds of Ga--N covalent bonds. The electron density at the saddle point of Ga--N bond parallel to [001] axis is 0.5, [e/Å
3]. On the other hand, that of the other three equivalent Ga--N bonds are 0.8, [e/Å
3]. Furthermore, it is found that the electron distribution of N atom shows asymmetric distortion. These features suggest asymmetric thermal vibrations of N atom which are restricted by Ga--N bonds.
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Toru Akiyama, Atsushi Oshiyama, Osamu Sugino
Subject area: Structure of liquids and solids; crystallography.
1998 Volume 67 Issue 12 Pages
4110-4116
Published: December 01, 1998
Released on J-STAGE: October 01, 1999
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We perform microscopic total-energy calculations based on a transferable tight-binding model combined with conjugate-gradient minimization technique for various multivacancies V
n in Si. We find that stable multivacancies (magic numbers of negative Si clusters) are V
6, V
10, V
14, V
17, V
22, V
26 and V
35. We also find that both topological networks of vacant sites and relaxation of surrounding atoms are crucial to determine energetics of the multivacancies.
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Hironori Nakao, Yasuhiko Fujii, Tetsu Watanuki, Kenji Ishii, Hiroyoshi ...
Subject area: Structure of liquids and solids; crystallography.
1998 Volume 67 Issue 12 Pages
4117-4123
Published: December 01, 1998
Released on J-STAGE: October 01, 1999
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Synchrotron x-ray powder diffraction experiments of a fullerene C
76 crystal have elucidated its structure and successive phase transitions for the first time.Two types of crystal lattices, fcc and hexagonal ones, coexist through the temperature range investigated between 10, K and 550, K. Both precise analysis of diffraction patterns as a functionof temperature and structural model calculations reveal successive phase transitions at 140 ± 10, K and 420 ± 10, K associated with degrees of molecular orientations for the hexagonal lattice.The fcc lattice undergoes a similar phase transition at 140 ± 10, K.By applying pressure and analyzing lattice constantswe also study compression and pressure-temperature phase diagramof this crystal.
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Shigefumi Yamamura, Masaki Takata, Makoto Sakata, Yoko Sugawara
Subject area: Structure of liquids and solids; crystallography.
1998 Volume 67 Issue 12 Pages
4124-4127
Published: December 01, 1998
Released on J-STAGE: October 01, 1999
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In order to explore the nature of the hydrogen bond, the electron density distribution of KH
2PO
4 (KDP) at room temperature was obtained by the maximum entropy method (MEM) using synchrotron radiation X-ray powder diffraction data. In the obtained electron density distribution maps, the contour lines linked the two oxygen atoms of neighboring PO
4 groups and a hydrogen-bonding network was clearly seen. However, no local maxima of electron density due to hydrogen atoms were recognized. This figure of hydrogen bonding in KDP is similar to that in ice (I
h), which is the only hydrogen-bonded compound previously analyzed by MEM. In both cases, the hydrogen atoms are believed to be disordered between the two oxygen atoms. The present study shows that the character of the hydrogen bond in crystalline materials can be described clearly by MEM, even in the case where heavier atoms such as K and P exist besides O atoms.
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Kangcheng Xu, Yang Chen
Subject area: Lattice dynamics and crystal statistics.
1998 Volume 67 Issue 12 Pages
4128-4130
Published: December 01, 1998
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A formula has been deduced, based on the simple binary ionic structure and fundamental concepts of lattice vibrations. It combines both the mass and interatomic distance effects. This model accounted well for the observed frequency shifts of the 52 and 84, cm
-1 bands of KNO
3 II in the solid solutions of RbNO
3 in KNO
3 II (denoted as K
1-xRb
xNO
3 (KII)). For ionic crystals containing planar NO
3-, our method appeared to work better than the lattice dynamic analysis based on the rigid ion model.
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In–Sung Park, Kenichi Saruta, Seiji Kojima
Subject area: Equations of state, phase equilibria, and phase transitions.
1998 Volume 67 Issue 12 Pages
4131-4138
Published: December 01, 1998
Released on J-STAGE: October 01, 1999
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In order to study the molecular weight dependence of the α-relaxation and glass transitions of intermediate glass-forming materials, the dielectric and thermal properties have been investigated in both liquid and supercooled liquid states. By means of modulated DSC at 10mHz and broadband dielectric spectroscopy in the frequency range from 10mHz to 10GHz, propylene glycol (PG) and its five oligomers (poly propylene glycol, PPG), which have the similar chemical structure but different molecular weights 76--4000 ,g/mol, were studied paying attention to their fragility and cooperativity. The fragility of PG and PPGs from the dielectric and thermal measurements was analyzed and compared using both the intermolecular cooperativity model and the Adam-Gibbs model. The Vogel-Fulcher energy and minimum configurational entropy were evaluated for PG and PPGs using the comparison method. Their values were related to the density of -OH end group and its intermolecular hydrogen bonding. The strength parameter decreased with increasing molecular weight indicating that PG monomer liquid is stronger than PPG liquids. The domain size at T
g, which was introduced by the Matsuoka's cooperativity model, was about 2 to 5 for PG and PPGs, increasing with molecular weight. The increase of the domain size in the vicinity of T
g was shown to be related to the larger non-exponentiality.
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Katsumi Hamano, Kiyoshi Abe, Toshiharu Mitsui
Subject area: Equations of state, phase equilibria, and phase transitions.
1998 Volume 67 Issue 12 Pages
4139-4146
Published: December 01, 1998
Released on J-STAGE: October 01, 1999
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Ferroelectric domain patterns which appear under three different quenching conditions have been studied by means of an etching technique. When a b-plate sample is quenched from above T
C, a three-dimensional pattern which varies dramatically along the thickness direction is often observed. When single-domain samples are quenched from temperatures between about T
C-30°C and T
C, the polarization reversal occurs locally and two-dimensional domain patterns are formed. The polarization reversal is caused by the depolarization field which appears during quenching even when the electrodes are short-circuited. When a single-domain sample is heated and quenched in the middle of the C-to-IC transition, the nucleated IC phase regions are converted to ferroelectric domains. These domains and those produced by the polarization reversal in the commesurate phase regions are superposed to one another and make up complicated domain patterns.
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Kiiti Siratori, Yasuaki Nakagawa, Hiroaki Kato, Mitsuhiro Motokawa
Subject area: Equations of state, phase equilibria, and phase transitions.
1998 Volume 67 Issue 12 Pages
4147-4150
Published: December 01, 1998
Released on J-STAGE: October 01, 1999
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Magnetization of K
2CuF
4, a typical 2-dimensional Heisenberg ferromagnet with the Curie point of 6.25, K, was measured in a wide range of temperature and magnetic field, 4--60, K and 0--150, kOe. Existence of the scaling type magnetic equation of state was confirmed in an intermediate region, between the critical region and the Curie-Weiss region, as in the case of EuS, 3-dimensional Heisenberg ferromagnet. The scaling indices, corresponding to β and γ in the critical region, are b = 0.06 and c = 1.32, different from those for EuS, b = 0.14 and c = 1.15. This difference was assumed to be due to the different dimensionality.
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Kazuhiro Sano, Yoshiaki Õno
Subject area: Electron states in condensed matter.
1998 Volume 67 Issue 12 Pages
4151-4156
Published: December 01, 1998
Released on J-STAGE: October 01, 1999
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We investigate the one-dimensional d-p model with the transfer energy t
pp between the nearest neighbor p sites by the numerical diagonalization method. By calculating the critical exponent K
ρ based on the Luttingerliquid relations and the paring correlation functions, we analyze the superconducting state induced by the effect of the large repulsion U
d at the Cu site in cooperation with the transfer energy t
pp.We obtain a phase diagram of the superconducting region on the filling n vs. U
d parameter plane. It shows that the superconducting region appears when U
d is largerthan a certain critical value which decreases with increasing n.The results of paring correlation functions suggest that a singlet paringbetween the nearest neighbor p sites is most relevant to thesuperconductivity. We also discuss a relationship between the d-p model and the t-Jmodel through an analysis of the dependence of K
ρ on theparameters.
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Thierry Ouisse
Subject area: Electron states in condensed matter.
1998 Volume 67 Issue 12 Pages
4157-4163
Published: December 01, 1998
Released on J-STAGE: October 01, 1999
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An analytical form of screened impurity potential is derived, taking into account the presence of a bound electron exhibiting a hydrogenic wave function. A subsequent calculation of the impurity level as a function of the screening parameter then shows that the impact of screening can become very different, depending on whether the impurity was initially occupied or empty. When the screening parameter exceeds the (unscreened) reciprocal Bohr radius, there is no empty impurity state, whereas if an electron is trapped there remains a localized state, the level of which saturates around 0.39, Ry. Possible implications of this result are discussed, regarding either neutral impurity scattering, the Metal-Insulator Transition or the possibility to get bistable impurity states.
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Shin–ichi Fujimori, Yasuharu Saito, Noriaki Sato, Takemi Komatsu ...
Subject area: Electron states in condensed matter.
1998 Volume 67 Issue 12 Pages
4164-4168
Published: December 01, 1998
Released on J-STAGE: October 01, 1999
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The XPS valence-band and core-level spectra of pseudo-binary U(Rh
1-xPd
x)
3 alloys for x=0, 0.83, 0.93, 0.97, and 1.0 were measured to investigate the systematics of their core-level spectra. We could consistently understand their U 4f core-level spectra by assuming three final-state configurations, like the core-level spectra of mixed-valence Ce-based compounds. These final states are ascribed to predominance of 5f
2-, 5f
3-, and 5f
4-configurations, which are caused by the mixed valence with 5f
2(U
4+) and 5f
3(U
3+) character in the initial state. The results indicate the possibility of determining the valence states of other uranium compounds from the analysis of their core-level spectra.
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Ko Sugihara, Keiko Matsubara, Itsuko S. Suzuki, Masatsugu Suzuki
Subject area: Electronic transport in condensed matter.
1998 Volume 67 Issue 12 Pages
4169-4177
Published: December 01, 1998
Released on J-STAGE: October 01, 1999
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The c-axis resistivity ρ
c and longitudinal magnetoresistance Δ ρ
cL/ρ
0 of MoCl
5 GIC's (stage-2 to 6) have been extensively studied theoretically in terms of the following series-resistance model: ρ
c≅ d
Iρ
c(GIG)+d
G(n-1)ρ
c(GG)/I
c, ρ
c(GG)=∑
i=1n-1ρ
GG(i, , i+1)/(n-1), where n is the stage number, ρ
c(GIG) is the partial resistivity related to graphite-intercalant-graphite sandwich layer and ρ
GG(i, , i+1) corresponds to the resistivity associated with the i↔ i+1 transition in an interior layer region without intervening intercalate layers. ρ
GG(i, , i+1) makes a bottleneck in the conduction process along the c-axis, and plays an essential role in the longitudinal negative magnetoresistance for stage-4 to 6 and in the stage dependence of ρ
c vs. T curve. By using the same model we can explain the metallic temperature dependence and positive magnetoresistance in the in-plane conduction which is independent of the stage number.
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Takuya Okabe
Subject area: Electronic transport in condensed matter.
1998 Volume 67 Issue 12 Pages
4178-4192
Published: December 01, 1998
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We develop a general theory of Fermi liquids to discuss the Kadowaki-Woods relation A∝ γ
2between the coefficient A of the T
2 term in the resistivity σ
-1=AT
2and γ of the specific heat C=γ T at low temperatures.We derive a formula for the ratio A/γ
2 which is expressed as a product of two dimensionless parameters α and F, where α represents a coupling constant for quasiparticle scattering and F is a geometric factor determined by the shape of the Fermi surface.Then we argue that the universal ratio A/γ
2=1.0× 10
-5 μ Ω cm(mol, K/mJ)
2observed in heavy fermion compounds is reproduced under the conditions α-- 1 and F-- 20. The former is regarded as a universality of Fermi liquids in a strong coupling regime, and the latter is corroborated byevaluating F definitely in simple cases.It is noted that the proportional relation is just an example of the universal phenomena to be expected forthe whole class of strong coupling Fermi liquids.
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G. K. Rohan Senadeera, Tadashi Kawamoto, Takehiko Mori, Jun–ichi ...
Subject area: Electronic transport in condensed matter.
1998 Volume 67 Issue 12 Pages
4193-4197
Published: December 01, 1998
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In an attempt to clarify the nature of the metal insulator transition of β -(BEDT-TTF)
2PF
6 family salts, temperature dependence of the static magnetic susceptibility, resistivity under various pressures, lattice parameters and the intensity of X-ray superlattice reflections have been measured for β -(BEDT-TTF)
2PF
6 and β -(BEDT-TTF)
2AsF
6. The transition temperature (T
MI) of these salts is shifted to higher temperatures with an increase of pressure. A sharp drop of the activation energy is observed at 5, kbar for the PF
6 salt and 6, kbar for the AsF
6 salt. Above these pressures, resistivity becomes almost flat down to low temperatures though the resistivity again increases below 50, K. Phase diagrams were constructed for both materials. Static magnetic susceptibilities of both salts exhibit abrupt drops below T
MI. A noticeable drop of the lattice parameters, lattice volumes and the X-ray intensities around T
MI indicate that the M-I transition is associated with the structural transition. The existence of the 2-fold structural changes is established by observing the superlattice reflections corresponding to (a, , b, , 2c) below T
MI.
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Yutaka Nakai
Subject area: Electronic transport in condensed matter.
1998 Volume 67 Issue 12 Pages
4198-4200
Published: December 01, 1998
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Electrical resistivities of β -Mn(Sn) alloys were measured. Resistivity minima were observed above the freezing temperatures. Extra resistivity is found besides resistivities due to impurity and atomic vibration, and it is expressed by a log T term.
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Atsushi Fukui, Hideaki Kasai, Ayao Okiji
Subject area: Electronic structure and electrical properties of surfaces, interfaces and thin films.
1998 Volume 67 Issue 12 Pages
4201-4208
Published: December 01, 1998
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A model calculation for the dissociative scattering of hydrogen molecules from metal surfaces is carried out with the aid of the Hubbard model for the metal substrate.The Coulomb interaction between electrons in the substrate is taken account of within the single-site approximation in calculating the probability distribution of the dissociative scattering.It is shown that the probability for the dissociative scattering of hydrogen molecules increases as the magnitude of the Coulomb interaction between electrons in the metal substrate is increased.
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Ken"ichi Takano, Kazuhiro Sano
Subject area: Magnetic properties and materials.
1998 Volume 67 Issue 12 Pages
4209-4212
Published: December 01, 1998
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We examine experimental magnetic susceptibility χ
tot(T) for CaV
4O
9 by fitting with fitting function α χ
mag(T) + c. The function χ
mag(T) is a power series of 1/T and the lowest order term is fixed as C/T, where C is the Curie constant as determined by the experimental g-value (g=1.96). Fitting parameters are α, c and expansion coefficients except for the first one in χ
mag(T). We determine α and c as α ~= 0.73 and c~= 0 for an experimental sample. We interpret α as the volume fraction of CaV
4O
9 in the sample and χ
mag(T) as the susceptibility for the pure CaV
4O
9. The result of α \
e 1 means that the sample includes nonmagnetic components. This interpretation consists with the result of a perturbation theory and a neutron scattering experiment.
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Izuru Umehara, Qingfeng Lu, Masato Endo, Yoshiya Adachi, Kiyoo Sato
Subject area: Magnetic properties and materials.
1998 Volume 67 Issue 12 Pages
4213-4217
Published: December 01, 1998
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The magnetic susceptibility, electrical resistivity and specific heat as a function of temperature have been investigated for Nd
3Co single crystal. Three transitions at 8.5K, 14K and 25K were observed. Furthermore, the complex metamagnetic transitions were observed in the magnetization curves along the a- and b-axes. These magnetization processes are explained by the pseudo-two-sublattice ferromagnetic model.
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Kichizo Asai, Kouji Fujiyoshi, Nobuhiko Nishimori, Yasumasa Satoh, Yos ...
Subject area: Magnetic properties and materials.
1998 Volume 67 Issue 12 Pages
4218-4228
Published: December 01, 1998
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Magnetic properties of REMe
0.5Mn
0.5O
3 with Me = Ni and Co are investigated for a series of rare earth (RE) elements. In both systems with Me = Ni and Co, the Curie temperature (T
C), below which the magnetic moments of Me
2+ and Mn
4+ allign ferromagnetically, decreases remarkably as RE goes from La to heavier elements; from 295 K for RE = La to 50 K for Lu with Me = Ni, and from 250 K for La to 95 K for Ho with Me = Co. The decrease of T
C is interpreted as due to the bond angle (θ) dependence of the superexchange interactions between Me
2+ and Mn
4+ through O
2-; T
C is roughly linear to cos
2θ as predicted by a simple theory [C. Boekema et al.: Int. J. Mag. 3 (1972) 341], but a distinct deviation from the linear relation is observed for the late RE elements. The magnetic moments of RE ions appears only in a low temperature region, typically below 30K. Qualitative discussion on the exchange interactions involving RE is presented.
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Tomohiko Kato, Kouki Kobuchi, Hidenori Kubo, Kazuko Zenmyo
Subject area: Magnetic properties and materials.
1998 Volume 67 Issue 12 Pages
4229-4234
Published: December 01, 1998
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Magnetic structures and phase transitions of CsMn
1-xCo
xCl
3· 2H
2O, a typical substance of random magnetic mixtures with competing magnetic anisotropy, are investigated theoretically by assuming a simplified model: classical 2-D X-Y model with the single-ion type anisotropy. The magnetic susceptibility for each easy axis and the thermal average of each spin are calculated by Monte-Carlo simulation. It results that the characteristic features of the phase diagram are reproduced, that is, besides the CsMnCl
3· 2H
2O-type antiferromagnetic phase and the CsCoCl
3· 2H
2O-type one, an intermediate phase exists in between the two phases. In the intermediate region, two successive phase transitions occur with increasing temperature. It is found that the spin structure of the intermediate phase has two perpendicular antiferromagnetic domains linked by domain walls. This result is consistent with the NMR experiments.
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Hisashi Sasaki, Hiroshi Harashina, Katsuaki Kodama, Masatoshi Sato, Sh ...
Subject area: Magnetic properties and materials.
1998 Volume 67 Issue 12 Pages
4235-4242
Published: December 01, 1998
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Magnetic excitation spectra of BaCo
1-xNi
xS
2, whichhas a layered structure and exhibits Mott metal-insulator (M-I) transition with varying x and/or with increasing external pressure, have been measured and analyzed. The random phase treatment has been found to be able to basically describe the observed dynamical magnetic behavior except in the temperature region where the intrinsic magnetic correlation length is larger than the average separation of Ni atoms. The characteristic energy of the spin fluctuation in two kinds of metallic phases induced by the Ni-doping and by the external pressure p are rather differrent. These results indicate that the pressure-induced Mott transition is mainly driven by the increase of the transfer energy, while the doping-induced transition is driven by the deviation of the electron number of each relevant band from unity.
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Osamu Suzuki, Terutaka Goto, Shintaro Nakamura, Takeshi Matsumura, Sat ...
Subject area: Magnetic properties and materials.
1998 Volume 67 Issue 12 Pages
4243-4250
Published: December 01, 1998
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We measured the elastic and thermal properties to examine the competing effect between the intersite interactions and the Kondo coupling in Ce
0.75La
0.25B
6 and Ce
0.6La
0.4B
6 with the Γ
8 ground state. The huge softening of the transverse C
44 mode of both compounds at low temperatures indicates a remarkable fluctuation of the quadrupolar moments O
yz, O
zx and O
xy with Γ
5 symmetry. In the magnetic phase diagram of Ce
0.75La
0.25B
6, we found a new ordered phase IV in addition to the antiferroquadrupolar phase II and the antiferromagnetic phase III. The compound Ce
0.6La
0.4B
6, however, shows the Fermi liquid state without the long-range order at low fields and transits into the ordered phase II or III in the magnetic field above 16kOe.
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Dai Aoki, Yasuhisa Katayama, Rikio Settai, Norihito Suzuki, Kiyohiro S ...
Subject area: Magnetic properties and materials.
1998 Volume 67 Issue 12 Pages
4251-4259
Published: December 01, 1998
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We observed the de Haas-van Alphen oscillations of a Pauli paramagnetic compound YbPb
3 and an antiferromagnetic compound EuPb
3. Detected Fermi surfaces in YbPb
3 are three in number, which are well explained by the FLAPW band calculations.The cyclotron effective masses are in the range from 0.21 to 0.60, m
0.The paramagnetic and antiferromagnetic Fermi surfaces were detected in EuPb
3.The former Fermi surface is the same as in YbPb
3, which is seen by magnetic breakdown.EuPb
3 is a divalent compound whose magnetic properties were studied by the specific heat, magnetic susceptibilityand high-field magnetization experiments.
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Kenjiro Hashi, Akira Oyamada, Satoru Maegawa, Takao Goto, Dexin Li, Ta ...
Subject area: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
1998 Volume 67 Issue 12 Pages
4260-4268
Published: December 01, 1998
Released on J-STAGE: October 01, 1999
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Nuclear magnetic resonance and relaxation studies on
75As in an Yb-monopnictide YbAs have been carried out at temperatures down to 20, mK to clarify the magnetic properties of this compound from a microscopic point of view. A notable result is that the spin-lattice relaxation rate 1/T
1 shows Fermi-liquid-like behavior given as (T
1T)
-1=2.9, (s, K)
-1 below 0.2K. The constant value of (T
1T)
-1 in YbAs is discussed using the Korringa relation for a single impurity model to compare with those in other heavy Fermion compounds. The NMR spectra between 0.4K and 0.6K indicate that the paramagnetic and the antiferromagnetically ordered regions coexist. From these results, it is found that YbAs is a heavy Fermion compound which undergoes an antiferromagnetic transition.
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Isao Yamada, Hirotaka Manaka, Hiroshi Sawa, Masakazu Nishi, Masahiko I ...
Subject area: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
1998 Volume 67 Issue 12 Pages
4269-4278
Published: December 01, 1998
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Electron spin resonance experiments were performed on α '-NaV
2O
5, a possible spin-Peierls compound, at 9.3 and 23.5 GHz over 1.3--700 K.Analyzing all factors of the absorption line above T
sp=34 K, such as the value and the angular dependence of the linewidth at high temperatures, the temperature dependence of both the linewidth and the resonance field, as well as the high temperature lineshape, we find that the exchange-narrowing theory closely explains these factors when a linear Heisenberg chain with S=1/2 along the b-axis is assumed, and the antisymmetric exchange interaction, ∑
id
i i+1·(S
i×S
i+1) with d
i+1//, c-axis, between nearest-neighbor spinson the b-axis is adopted as the origin of line broadening. As long as the results of this study are concerned, the model of V
4+ magnetic chains separated by nonmagnetic V
5+ chains in the ab-plane above 34 K is acceptable.However, the results do not necessarily deny a V-O-V molecular spinmodel that has been proposed to account for a new crystal structure formedby only one distinct V site, because the molecular spin model, as shown in recent theoretical papers, leads to antiferromagnetic Heisenberg linear chains along the b-axis. If an effective antisymmetric exchange interaction between the molecular spins is proven to exist, it can be an origin of the line broadening of this compound.
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Akira Hori, Tetsuya Tada, Kaoru Kimura
Subject area: Optical properties and condensedmatter spectroscopy and other interactions of matter with particles and radiation.
1998 Volume 67 Issue 12 Pages
4279-4284
Published: December 01, 1998
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We report the detailed features of the photoluminescence (PL) spectra of a single crystal of β -rhombohedral boron (β -B) in the range of 900--1700, nm (0.73--1.38eV). Broad spectra whose peak energy was 1.14eV were observed. The peak energy corresponds to the recombination of an electron in a trapping level with a hole in the intrinsic acceptor level, which is characteristic of β -B and originates from the unique electronic structure of an icosahedral cluster B
12. Temperature dependence of the PL intensity indicates that there are two thermal escape processes of electrons whose activation energies are about 0.10 and 0.004eV. The former is attributed to the escape process of an electron from the electron trapping level to the conduction band. These results agree with the proposed band structure model based on the electronic structure of B
12. PL decay measurement shows that there are two components with lifetimes of 4× 10
-7s and 5× 10
-5s.
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Ariete Righi, Patrice Bourson, Alejandro Pedro Ayala, Marcos Assun&cce ...
Subject area: Optical properties and condensedmatter spectroscopy and other interactions of matter with particles and radiation.
1998 Volume 67 Issue 12 Pages
4285-4290
Published: December 01, 1998
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The structural phase transitions of the LiK
0.50Rb
0.50SO
4 mixed crystal were investigated by Raman spectroscopy and neutron powder diffraction up to 800, K. The results show two first order structural transitions, quite analogous to the transitions in LiKSO
4. Raman spectra and diffraction profiles were compatible with average symmetries C
3v4, C
66 and D
2h16 for the three observed phases, with increasing temperature. The transitions, both reconstructive, are smeared over large temperature intervals, leading to the coexistence of Raman bands and neutron peaks of the different phases and to an anomalous behavior of the lattice parameters into these intervals. In the hexagonal phase, the cell volume presents a hysteretic behavior depending on the sample thermal history. Raman spectra of the orthorhombic phase shows the high rotational disorder of the SO
4 ions, associated with the high Li positional disorder in this high conducting phase.
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Makoto Matsumoto, Maki Tokii, Shinya Wakoh
Subject area: Optical properties and condensedmatter spectroscopy and other interactions of matter with particles and radiation.
1998 Volume 67 Issue 12 Pages
4291-4295
Published: December 01, 1998
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Spin magnetic form factors of hcp cobalt are calculated by the APW method using the SDF potential. The results are compared with the experimental values obtained by neutron diffraction and recent white beam method of x-ray magnetic diffraction.
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Elaheh K. Goharshadi, Zahra MirAfzali, Zahra Tavangar
Subject area: Physical chemistry.
1998 Volume 67 Issue 12 Pages
4296-4299
Published: December 01, 1998
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The pair-potential energy functions SF
6-noble gases have been determined from a direct inversion of the experimentally reduced-viscosity collision integrals obtained from the corresponding states correlation. The resulting potentials are in an excellent agreement with the previously determined potentials. The collision integrals and thier ratios of these potentials which are necessary to calculate the theoretical values of transport coefficients are computed. The collision integrals have been used to predict the diffusion coefficients of the binary mixtures of hexafluoride with noble gases. The results indicate the agreement between theory and experiment is within the experimental uncertainties.
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Koji Imai, Kimiaki Konno, Hiroshi Kakuhata
Subject area: Mathematical methods in physics.
1998 Volume 67 Issue 12 Pages
4300-4301
Published: December 01, 1998
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