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Hiroshi Kakuhata, Kimiaki Konno
Subject area: Mathematical methods in physics.
1996 Volume 65 Issue 1 Pages
1-2
Published: January 01, 1996
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Starting from the Lagrangian of coupled integrable, dispersionless equations, we derive the Hamiltonian. Conserved quantities associated with the symmetries of the Lagrangian are obtained, which cannot be derived by the inverse scattering method.
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Hidetoshi Nishimori, Michiko Yamana
Subject area: Statistical physics and thermodynamics.
1996 Volume 65 Issue 1 Pages
3-6
Published: January 01, 1996
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The microscopic probability distribution function of the Sherrington-Kirkpatrick (SK) model of spin glasses is calculated explicitly as a function of time by a high-temperature expansion. The resulting formula to the third order of the inverse temperature shows that an assumption made by Coolen, Laughton and Sherrington in their recent theory of dynamics is violated. Deviations of their theory from exact results are estimated quantitatively. Our formula also yields explicit expressions of the time dependence of various macroscopic physical quantities when the temperature is suddenly changed within the high-temperature region.
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Hiroyasu Ejiri, Hiroshi Toki
Subject area: Nuclear decay and radioactivity.
1996 Volume 65 Issue 1 Pages
7-10
Published: January 01, 1996
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Nuclear matrix elements M
2ν for two-neutrino double beta decays in medium-heavy even nuclei are found to be given by a product of matrix elements M
νS M
ν_{S'} for successive single beta decays through low-lying single particle-hole 1
+ states in intermediate nuclei. The empirical systematics is explained theoretically by coupling of single particle-hole 1
+ states with GT (Gamow Teller) giant resonances.
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Masatoshi Yagi, Atsushi Fukuyama, Sanae–I. Itoh, Kimitaka Itoh
Subject area: Kinetic and transport theory of fluids; physical properties of gases.
1996 Volume 65 Issue 1 Pages
11-13
Published: January 01, 1996
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Based on the anomalous transport model due to current diffusive ballooning mode turbulence, the global energy confinement time in a tokamak with Ohmic heating is theoretically studied. Relations to empirical scaling laws are also discussed.
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Kazuo Gesi, Makoto Iwata, Yoshihiro Ishibashi
Subject area: Equations of state, phase equilibria, and phase transitions.
1996 Volume 65 Issue 1 Pages
14-15
Published: January 01, 1996
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The low-temperature dielectric anomalies of two isomorphic ferroelectrics (CH
3NH
3)
5Bi
2Cl
11 (MAPCB) and (CH
3NH
3)
5Bi
2Br
11 (MAPBB) have been studied in detail. The anomaly in the dielectric constant of MAPBB at 77K shows a thermal hysteresis along all three crystallographic axes. The broad peak of the dielectric constant along the a-direction of MAPCB around 160K becomes flatter and more diffuse as pressure increases. It is concluded that the 77K anomaly in MAPBB represents a first-order phase transition whereas the 160K anomaly in MAPCB is an over-critical phenomenon of an isomorphous transition.
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Yasunori Kubo
Subject area: Electron states in condensed matter.
1996 Volume 65 Issue 1 Pages
16-18
Published: January 01, 1996
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The Compton profile of Li is computed by using the occupation number obtained from a first-principles calculation of the spectral function within the GW approximation (GWA). The eigenstates and eigenenergies generated by the full-potential linearized augmented-plane-wave method in the local-density approximation are utilized in the GWA calculation. The dielectric matrix needed to form the screened potential W is computed within the random-phase approximation. The computed Compton profiles are in very good agreement with recent experimental results measured with a momentum resolution of 0.12 atomic units.
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Yoshiaki Ono
Subject area: Electron states in condensed matter.
1996 Volume 65 Issue 1 Pages
19-22
Published: January 01, 1996
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We investigate magnetization as a function of external magnetic field H in the U-infinite Anderson lattice model within the leading-order approximation in the 1/N-expansion. At T=0, at H=H
M where the Zeeman energy is equal to a certain characteristic energy of the system, the magnetization curve has a kink and the differential susceptibility d M/d H shows a jump. At finite temperature, d M/d H shows a peak around H
M. Its maximum value increases with decreasing T and saturates to a finite value at T→ 0. When H
M, the f and conduction electrons form renormalized bands with a large Fermi surface determined by the Luttinger sum rule.On the other hand, when H>HM, the bands reform such that they are free from the Luttinger sum rule, eventually leading to a small Fermi surface at H >> HM.These results are consistent with the metamagnetic properties observed in the heavy fermion compound CeRu2Si2.
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Mitsuru Sugisaki, Osamu Arimoto, Kaizo Nakamura
Subject area: Electron states in condensed matter.
1996 Volume 65 Issue 1 Pages
23-26
Published: January 01, 1996
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Detailed excitation spectra for singlet and triplet luminescence in ZnP
2 are observed at 2 K by using a Ti:sapphire laser.When a singlet exciton is excited, conversion to a triplet exciton occurs over a wide excitation energy range.The spin memory of the exciton is easily lost under the band-to-band excitation condition.When the triplet exciton is excited, the excitation spectrum for the triplet luminescence shows a clear hydrogen-like series up to n=9, which reflects the absorption spectrum of a spin triplet exciton series with s-d doublet structure for n≥q 3.The excitation spectrum for the singlet luminescence under the excitation of the triplet exciton is observed for the first time as a new exciton series appearing only for n≥q 3.The new exciton series results from the contribution of the d-envelope function of the exciton, and the s-envelope function alone does not give rise to the singlet luminescence.
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Yoshiya Uwatoko, Takayuki Ishii, Gendo Oomi, Hiroki Takahasi, Nobuo Mo ...
Subject area: Electronic transport in condensed matter.
1996 Volume 65 Issue 1 Pages
27-29
Published: January 01, 1996
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The effect of pressure on the electrical resistivity of CeRhSb has been studied up to 80kbar in order to elucidate the electronic Properties of CeRhSb at low temperature. It is found that the Kondo temperature increases with pressure and gap is quenched at P=80kbar, showing a maximum around 30kbar.
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Arisato Kawabata
Subject area: Electronic transport in condensed matter.
1996 Volume 65 Issue 1 Pages
30-32
Published: January 01, 1996
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A simple explanation is given for the renormalization factor of the conductance in one-dimensional interacting electron systems.Within the Tomonaga-Luttinger model, it is shown that the factor arises fromthe renormalization of electric potential, and that the conductance is not renormalized if we define it correctly. The theory is valid even when the interaction ispresent over the entire system.
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Ryusuke Ikeda
Subject area: Superconductivity.
1996 Volume 65 Issue 1 Pages
33-35
Published: January 01, 1996
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It is shown that, within a Ginzburg-Landau (GL) formalism, the superconducting fluctuation is insulating at zero temperature even if the fluctuation dynamics is metallic (dissipative). Based on this result, the low-temperature behavior of the H
c2-line and the resistivity curves near a zero-temperature transition are discussed. In particular, it is pointed out that the neglect of quantum fluctuations in data analysis of the dc resistivity may lead to an underestimation of the H
c2 values near zero temperature.
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Ryuta Yagi, Takahide Yamaguchi, Hideto Kazawa, Shun–ichi Kobayas ...
Subject area: Superconductivity.
1996 Volume 65 Issue 1 Pages
36-38
Published: January 01, 1996
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We studied the phase diagram for superconductor-insulator (S-I) transitions in a two-dimensional network of Al/AlO
x/Al Josephson junctions by varying the tunneling resistance R
n and by varying the junction area of the tunneling junction S from 0.01μm
2 to 0.09μm
2. We observed that the critical tunneling resistance exhibited significant S-dependence and the resultant phase diagram was reminiscent of that of Fazio and Schön's theory. We also observed some differences between the results of theory and experiment at large E
J/E
C values.
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Makoto Yajima, Minoru Takahashi
Subject area: Magnetic properties and materials.
1996 Volume 65 Issue 1 Pages
39-42
Published: January 01, 1996
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The successive phase transitions of the Heisenberg spin chain with bond alternation, {\cal H} = ∑_{i=1}
L-1[1-(-1)^i δ]{S} _i · {S}
i+1, for the spin S=3/2 case under the open boundary condition are investigated by the density-matrix renormalization-group method proposed by White. Besides the Heisenberg point, we find that another gapless point exists at δ
c = 0.42 ± 0.02.This result qualitatively supports the field-theoretical prediction by Affleck and Haldane.However, our estimation of δ
c deviates from the field-theoretical prediction, δ
c = 2/3. We also find a fourfold degeneracy of the ground state in the region 0 <δ< δ
c in the thermodynamic limit.Our results show that the degeneracy is described by the edge excitations, which is essentially similar to the one in the S=1 case.We calculate the string correlation function and find that its behavior is consistent with the valence-bond-solid (VBS) picture.
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Shin–ichiro Kondo, Masayuki Hasaka, Takao Morimura
Subject area: Magnetic properties and materials.
1996 Volume 65 Issue 1 Pages
43-45
Published: January 01, 1996
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We examine the magnetic behaviors of a single-domain particle with uniaxial magnetic anisotropy using Monte Carlo simulation for the purpose of investigating our proposed method (i.e. magnetic analysis on the basis of the discrete Markov process). Magnetic behaviors such as those of M-H curves and coercive forces calculated by Monte Carlo simulations are in good agreement with those calculated by the discrete Markov process, even though the methods are based on different ideas and procedures; thus analysis based on the discrete Markov process is considered to be very useful for investigating the magnetic behaviors of a single-domain particle with uniaxial magnetic anisotropy under the assumption used in Stoner-Wohlfarth theory.
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Kazuhiro Sano, Ken’ichi Takano
Subject area: Magnetic properties and materials.
1996 Volume 65 Issue 1 Pages
46-49
Published: January 01, 1996
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We examined a two-dimensional Heisenberg model with two exchange energies, J
e and J
c. This model describes localized spins at vanadium ions in a layer of CaV
4O
9, for which a spin gap was found by a recent experiment. Comparing the high-temperature expansion of the magnetic susceptibility with experimental data, we determined the exchange energies as J
e≅ 610K and J
c≅ 150K. By numerical diagonalization we estimated the spin gap as Δ-- 0.2J
e≅ 120K, which is consistent with the experimental value of 107K. Frustration by finite J
c enhances the spin gap.
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Hiroshi Yamamoto, Masayasu Ishikawa
Subject area: Magnetic properties and materials.
1996 Volume 65 Issue 1 Pages
50-52
Published: January 01, 1996
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A gradual change from the Kondo lattice to the impurity Kondo regime has been observed in Ce
1-xLa
xFeGe
3 (x=0, 0.1, 0.3, 0.5, 1.0). CeFeGe
3 exhibits a greatly reduced resistivity below about 100, K corresponding to the coherent state of the Kondo lattice. Ce
0.5La
0.5FeGe
3, on the other hand, shows a resistance minimum around 30K which is consistent with the impurity Kondo regime. The ground state of CeFeGe
3 turns out to be very stable against the La substitution and no magnetic instability is induced in the present diluted system.Magnetic susceptibility at 0, K per mole of Ce, χ (0), and the linear term of the specific heat, γ increase by 24% and 15% from x=0.0 to 0.5, respectively. The Kondo temperatures T
K's estimated from χ (0) and γ decrease accordingly by 20 and 13% in the same range of La content. This decrease in T
K is explained by the lattice expansion caused by the substitution of La for Ce.
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Kenji Imai, Kazuhiro Nozaki
Subject area: Mathematical methods in physics.
1996 Volume 65 Issue 1 Pages
53-57
Published: January 01, 1996
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Recently we presented (2+1) dimensional soliton equations covariant with respect to the Darboux transformation, including the Davey-Stewartson (DS) -II equation, the Ishimori-II equation and so on. In this paper we introduce the binary Darboux transformation in a auxiliary linear system and derive systematically (2+1) dimensional soliton equations covariant with respect to the binary Darboux transformation, which include not only the DS-I equation and the Ishimori-I equation but also a (2+1) gemeralization of the modified K-dV equation and so on.
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Taichiro Takagi
Subject area: Mathematical methods in physics.
1996 Volume 65 Issue 1 Pages
58-63
Published: January 01, 1996
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New polynomial identities are presented in a context of statistical mechanics.They are associated with the one-dimensional configuration sums of thecorner transfer matrix calculation of the solvablevertex models.In the infinite order limit they producewell-known principally specialized character formulas of level 1 modules of affine Lie algebras A
n(1), B
n(1)and D
n(1).
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Yoshiki Hidaka, Hiroshi Orihara, Yoshito Miyazaki, Tomoyuki Nagaya, Yo ...
Subject area: Statistical physics and thermodynamics.
1996 Volume 65 Issue 1 Pages
64-69
Published: January 01, 1996
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The formation processes of a one-dimensional periodic pattern were investigated on the electro-hydrodynamic convection of a nematic liquid crystal. Two kinds of processes for different initial conditions were observed. In the first initial condition the system was set to be the no-flow state in the absence of the applied field, and in the second the turbulent state under a strong field. The temporal change of the one-dimensional image intensity was measured after the amplitude of an ac electric field was jumped from these initial values to a value slightly above the critical one. The power spectrum function and the locally varying phase were calculated from the image intensity. The obtained results were compared with the numerical simulations of the diffusion equation.
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Toshiya Iwai
Subject area: Statistical physics and thermodynamics.
1996 Volume 65 Issue 1 Pages
70-76
Published: January 01, 1996
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Dynamics of a traveling kink in the presence of a localized quenched impurity is investigated both numerically and analytically for one-dimensional system described by the Nagumo equation without the thermal noise. We find the following results. (i) The interaction between the traveling kink and the impurity is attractive. (ii) If the impurity effect is weak, the traveling kink passes through the impurity position and the phase shift of the trajectory of the kink position from that of the unperturbed motion takes a positive or negative value depending on both the impurity effect and the velocity of unperturbed motion. (iii) If the impurity effect is strong, the traveling kink is pinned by the impurity position. (iv) When the distance between the traveling kink and the impurity is large, a spiky defect is formed in the order parameter profile at the impurity position.
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Yusuke Kato, Yoshio Kuramoto
Subject area: Statistical physics and thermodynamics.
1996 Volume 65 Issue 1 Pages
77-86
Published: January 01, 1996
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We show by microscopic calculation that thermodynamics of the multicomponent Sutherland model is equivalent to that of a free particle system with fractional exclusion statistics at all temperatures. The parameters for exclusion statistics are given by the strength of the repulsive interaction, and have both intra- and inter-species components. We also show that low temperature properties of the system are described in terms of free fractional particles without the statistical parameters for different species. The effective exclusion statistics for intra-species at low temperatures depend on polarization of the system.
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Takashi Fujikawa
Subject area: Molecular spectra and interactions of molecules with photons.
1996 Volume 65 Issue 1 Pages
87-94
Published: January 01, 1996
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The effect of atomic displacement on EXAFS after the core hole production is studied within the harmonic approximation for atomic vibration and single scattering approximation for the photoelectron wave. With aid of the Schwinger method, we obtain the Debye-Waller factor, the Condon factor and their interference term. The second term gives the damping of EXAFS and energy shift of the inner potential, and the last term gives rise to a phase factor as a linear function of photoelectron momentum k. The Condon factor and the interference term cancel each other as far as the side band effects are included, though each contribution is not negligible. Therefore the validity of the widely used Debye-Waller factor within the harmonic approximation is confirmed at least in EXAFS region. Numerical calculation estimates the order of those factors, and shows that the energy shift is negligibly small.
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Munefumi Shimbo, Atsunori Danjo
Subject area: Atomic and molecular collision processes and interactions.
1996 Volume 65 Issue 1 Pages
95-99
Published: January 01, 1996
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Ejected electron spectra from the autoionizing state in Na
+--He collisions have been measured with incident Na
+ ion energies from 1keV to 2.25keV. The anisotropy parameter β
2 for electron ejection from the autoionizing state Na(2p
53s
2)
2P is presented. The alignment of the autoionizing state is discussed in relation to the energy dependences of the anisotropy parameter β
2. The energy dependence of the anisotropy parameter β
2 is interpreted as being due to an excitation by a radial coupling between two ∑ states, followed by a full rotation of the quasimolecule during the slow Na
+--He collisions.
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Masahiro Nakagawa
Subject area: Fluid dynamics.
1996 Volume 65 Issue 1 Pages
100-106
Published: January 01, 1996
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In this work we shall present a hydrodynamic theoretical framework of compressible SmC
* liquid crystals. In practice we shall derive a set of the simultaneous nonlinear constitutive equations which may be regarded as an extension of the incompressible case. It is found that the present theory involves 17+4
* (
*: chiral) elastic constants and 25 viscosity coefficients for compressible SmC
* phase, which will be found to be eventually reduced to 9+2
* and 20, respectively, for incompressible case in consistence with the previous works. It is also shown that the layer normal unit vector and the compressibility scalar function have to be related each other through the Lagrange multiplier so as to assure the curlless field related to the conservation law of the number of layers.
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Yasuhide Fukumoto, Takeshi Miyazaki
Subject area: Fluid dynamics.
1996 Volume 65 Issue 1 Pages
107-113
Published: January 01, 1996
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We investigate the linear stability of regions of two-dimensional steady irrotational flows in which streamlines are closed, with respect tothree-dimensional perturbations of short wavelengths. The fluid is assumedto be inviscid and incompressible. The geometrical optics equations derived by Hameiri and Lifschitz are employed.It is demonstrated that, at large times, both short-waveperturbation velocity and vorticity grow in magnitude at most linearly in time. It implies that there are no exponentially growing short-wave instabilities in such a flow domain. The same result holds if the flow field is steady relative to a suitably chosen steadily rotating frame and the net vorticity relative to the inertial frame is zero.
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Akihide Takeda, Nobuaki Ikuta
Subject area: Kinetic and transport theory of fluids; physical properties of gases.
1996 Volume 65 Issue 1 Pages
114-123
Published: January 01, 1996
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In order to understand the effects of anisotropic scatterings on the electron transport properties, a trajectory analysis using extended FTI method has been performed in CF
4. A model anisotropy in the form g(χ )=1+a· cosχ with adjustable parameter “a” is assumed in each of elastic and inelastic scatterings. A clear correspondence has been found between the fractional changes of transport properties due to anisotropies in elastic and inelastic scatterings and the anisotropy in the velocity distribution of electrons in flight.
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Akira Yoshizawa
Subject area: Kinetic and transport theory of fluids; physical properties of gases.
1996 Volume 65 Issue 1 Pages
124-132
Published: January 01, 1996
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A transport equation for the turbulent residual helicity is studied for the self-consistent determination of the alpha dynamo effect. For this purpose, a simplified method for analyzing transport effects on mean-field magnetohydrodynamics is presented. Using this method, the mathematical structure of the turbulent residual-helicity equation is examined and its model equation obeying the least minimum requirements is discussed.
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Tomohiro Morisaki, Akio Komori, Kazuo Toi, Akira Ando, Akira Ejiri, Ka ...
Subject area: The physics of plasmas and electric discharges.
1996 Volume 65 Issue 1 Pages
133-138
Published: January 01, 1996
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Simultaneous measurements of electron density and its fluctuations were performed successfully in the CHSedge plasma during the L-H transition with a thermal neutral lithiumbeam probe. Very rapid formation of edge particle transport barrier within 0.1 msec was observed at the L-H transition, i.e., steepening of the edge electron density profile and reduction of the outward particle flux. The reduction of the fluctuation amplitude was also observed in the edgeregion, which was thought to be related to the formation of the edgeparticle transport barrier.
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Katsumi Hirano, Hiroyuki Kitaoka
Subject area: The physics of plasmas and electric discharges.
1996 Volume 65 Issue 1 Pages
139-141
Published: January 01, 1996
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Soft X-rays emitted from a plasma focus in which -- 1MA is discharged in argon admixed hydrogen are investigated for the development of a new X-ray source. A time resolved soft X-ray pinhole image near 4Å of the Ar K-lines and dynamic behavior of the plasma are observed simultaneously. It is found that the soft X-ray images can be typically divided into three categories in spite of the identical experimental condition. This fact makes the soft X-ray emission from the plasma focus device not reproducible. One category shows a highly conspicuous and filamentary source whose radius is -- 0.5mm, whereas the radius observed by the Moiré Schlieren technique is -- 1.5mm. The filament has a brightness several times greater than that of the other categories. Finally, the plasma in each of soft X-rays category is disrupted by growth of the m=0 instabilities. The plasma sustaining time was shorter than the characteristic time for the radiation collapse. The Pease-Braginskii current was evaluated to be 0.8MA. It was concluded that the radiative collapse did not occur although the discharge current exceeded the Pease-Braginskii current.
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Katsumi Hamano, Jialiang Zhang, Kiyoshi Abe, Toshiharu Mitsui, Hideaki ...
Subject area: Equations of state, phase equilibria, and phase transitions.
1996 Volume 65 Issue 1 Pages
142-148
Published: January 01, 1996
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The process of domain pattern coarsening in sodium nitrite has been studied by microscopic observation. The domain pattern was delineated by rubbing the b-face on deer's buff wetted with ethanol. Starting from a nearly one-dimensional domain pattern whose average domain width is 0.6μmthe pattern coarsens initially through nucleation and growth of antistripples. The antistripples are shaped like a dagger elongated in the b-direction. They are nucleated even between two adjacent walls separated as wide as 2μm. In the late stage the pattern coarsens through the backward motion of the fronts of wedge-shaped domains which have been formed by combined growth processes of antistripples. The sidewise motion of the planar walls was not observed in either of the initial or late stage. The one-dimensional character of the pattern is retained throughout the whole coarsening process.
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Jialiang Zhang, Katsumi Hamano, Kiyoshi Abe, Toshiharu Mitsui, Hideaki ...
Subject area: Equations of state, phase equilibria, and phase transitions.
1996 Volume 65 Issue 1 Pages
149-155
Published: January 01, 1996
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The average domain width, z, was chosen as the characteristic length of the nearly one-dimensional domain pattern of sodium nitrite. Its time evolution was obtained by measuring the time evolution of the strength of dielectric dispersion originating from domain wall motion. The time evolution of z was found to obey the power law z∝ (t+t
0)
α where α =1/3 and t
0 is a constant. The structure function, I
k, of the pattern was calculated by the Fourier-transform of the domain pattern. I
k shows a sharp peak at k=0, which implies that the volume occupied by the positive domains and that occupied by the negative domains are not equal. In addition, it shows a maximum around k\bar{z}=1-- 2. The role of electrostatic energy in the coarsening of pattern is discussed.
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Takashi Takahashi, Noriaki Sato, Takayoshi Yokoya, Ashish Chainani, Ta ...
Subject area: Electron states in condensed matter.
1996 Volume 65 Issue 1 Pages
156-159
Published: January 01, 1996
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Comparative high-resolution temperature-dependent photoemission measurements were performed for UPd
2Al
3 and UPd
3. The photoemission spectrum near E
F of UPd
2Al
3 consists of a sharp peak at E
F and a broad band at 0.5--1.0, eV binding energy, both features having U 5f character. The sharp feature at E
F shows good agreement with a recent band structure calculation, while the broad band matches well with the U 5f-derived localized feature in UPd
3, indicating the dual character of 5f electrons in UPd
2Al
3. The intensity of the broad band relative to the E
F-peak increases with increasing temperature, suggesting that the localized character of 5f electrons in UPd
2Al
3 increases at higher temperatures. These observations are consistent with the transport and magnetic measurements which imply a temperature-dependent dual (itinerant and localized) character of U 5f electrons in UPd
2Al
3.
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Tadao Kasuya, Masafumi Sera, Yasushi Okayama, Yoshinori Haga
Subject area: Electron states in condensed matter.
1996 Volume 65 Issue 1 Pages
160-171
Published: January 01, 1996
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Anomalous behavior of Hall constant and magnetoresistance in CeSb and CeBi under high magnetic field and high pressure is studied critically. At first, anomalous field dependence in the reference systems LaSb and LaBi is investigated based on the three band model in which two kinds of electrons are treated independently and it is concluded that the anomalous behavior is due to a small deviation from the stoicheometry, which is enhanced by a large mobility. In CeSb without pressure, no anomalous Hall effect is observed even in the ferromagnetic state. On the other hand, the normal Hall constant in CeSb and CeBi shows strong electron scattering in the whole temperature region confirming the model that the electrons also substantially contribute to the Γ
8 Kondo state. To study the anomalous Hall effect under high pressure and high magnetic field, general equations for anomalous Hall effect under high magnetic field are derived, and the anomalous Hall effect is identified to exit in the region in which a kind of magnetic polaron crystallization is thought to occur causing a sharp increase in resistivity. This is thought to be due to the direct 4f motion, similar to those in the mixed valence regime and the intermediate region in CeP and CeAs.
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Hiroshi Kontani, Kosaku Yamada
Subject area: Electron states in condensed matter.
1996 Volume 65 Issue 1 Pages
172-188
Published: January 01, 1996
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In the orbitally degenerate (J= 5/2) Periodic Anderson Model, the magnetic susceptibility is composed of boththe Pauli term and the Van Vleck term, as is well known.The former is strongly enhanced by the strong correlation between f-electrons.But, for the latter, the influence of the strong correlationhas been obscure for years.In this paper we give the solution of the longstanding problem.With the aid of the d=∞ approximation, we study this problem on the basis of the Fermi liquid theorywith degenerate orbitals, taking account of all the vertex correctionsin a consistent way.As a result, we obtain the simple expression for the magnetic susceptibility, and show unambiguously thatthe Van Vleck term is also highly enhanced in the strong correlation regime.This fact explains naturally the enhanced magnetic susceptibility observed in many insulating systems (i.e., Kondo insulator).Moreover, we show that the Wilson ratio takes a value around 1 in the metallic system, in good agreement with experiments.
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Fakher F. Assaad, Masatoshi Imada
Subject area: Electron states in condensed matter.
1996 Volume 65 Issue 1 Pages
189-194
Published: January 01, 1996
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We present a numerically stable Quantum Monte Carlo algorithm tocalculate zero-temperature imaginary-time Green functions G(r, τ) for Hubbard type models.We illustrate the efficiency of the algorithm by calculatingthe on-site Green function G(r=0, τ) on 4 × 4 to 12 × 12 latticesfor the two-dimensional half-filled repulsiveHubbard model at U/t = 4. By fitting the tail of G(r=0, τ) at long imaginary timeto the form e
-τΔc, we obtain a precise estimateof the charge gap: Δ
c = 0.67 ± 0.02 in units of the hopping matrix element. We argue that the algorithm provides a powerful tool to study the metal-insulatortransition from the insulator side.
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Norikazu Tomita, Atsushi Ikawa, Hideo Fukutome
Subject area: Electron states in condensed matter.
1996 Volume 65 Issue 1 Pages
195-206
Published: January 01, 1996
Released on J-STAGE: October 01, 1999
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We study the SDW-CDW phase transition in the one dimensional extended Hubbard model at a half-filling. A scaling analysis using the resonating Hartree-Fock method with the numbers of electrons from 8 to 20 strongly suggests that the ground state is many-fold degenerate(
1A
1+,
1B
1+,
3A
2-, and
3B
2- states) in the SDW region while it is doubly degenerate(
1A
1+ and
1B
2- states) in the CDW region. Only the
1A
1+ state makes a continuous phase transition from the SDW state to the CDW one. The
1B
1+,
3A
2-, and
3B
2- states cross the
1B
2- state around the phase boundary.We show that the continuous phase transition in the
1A
1+ state is brought about by defects connecting the SDW-CDW domains called halfons. The correlation structures of these states are shown to clarify the origin of the degeneracies of the ground states.
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Tetsuya Katano, Nobuo Tsuda
Subject area: Electronic transport in condensed matter.
1996 Volume 65 Issue 1 Pages
207-212
Published: January 01, 1996
Released on J-STAGE: October 01, 1999
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The Seebeck coefficient S of Ca
1-xSr
xRuO
3 (0≤ x≤ 1) was measured in the temperature range 78K to 300K. This coefficient always showed a large bend at about 160K, irrespective of the magnetic properties of the sample studied. The differential temperature coefficient dS/dT was found to decrease above this temperature (S>0). The usual single-band theory cannot explain this large bend, and we propose a percolation model in which metallic paths are composed of parallel-spin arrays, and semiconducting paths are composed of antiparallel-spin arrays.
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Takahiko Sasaki, Hiroaki Ozawa, Hatsumi Mori, Shoji Tanaka, Tetsuo Fuk ...
Subject area: Electronic transport in condensed matter.
1996 Volume 65 Issue 1 Pages
213-220
Published: January 01, 1996
Released on J-STAGE: October 01, 1999
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We have synthesized a new organic conductor α -(BEDT-TTF)
2KHg(SeCN)
4 which is found to be isostructural with a family of α-(BEDT-TTF)
2MHg(SCN)
4 with M=K, Tl, Rb and NH
4, where BEDT-TTF is bis(ethylenedithio)tetrathiafulvalene. In contrast to superconducting (M=NH
4) or antiferromagnetic (M=K, Tl, Rb) salts, the title compound remains a normal metal in the same way as α-(BEDT-TTF)
2TlHg(SeCN)
4.The magnetoresistance and the Shubnikov-de Haas (SdH) effect have been measured at temperatures down to 0.5K and magnetic fields up to 23T. The SdH frequency of 670T, the effective mass of 2.0m
0, and the Dingle temperature of 1.6K are obtained in fields perpendicular to the conductive a-c plane. The magnetic field direction dependence of the frequency shows that the observed Fermi surface has a cylindrical shape. The temperature and the field dependence of the SdH oscillation amplitude are well explained by the standard Lifshitz-Kosevich formulation, indicating that the effective mass is essentially constant up to 23T.
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Eisuke Iguchi, Takashi Hashimoto, Shino Yokoyama
Subject area: Electronic transport in condensed matter.
1996 Volume 65 Issue 1 Pages
221-229
Published: January 01, 1996
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In order to disentangle the confused arguments as to whether a band conduction or a hopping conduction dominates the electrical transport in Li
xCo
1-xO, dielectric properties, dc and ac conductivities, and thermopowers were investigated. Positive thermopowers indicated the major carriers of holes. Two dielectric relaxations appeared in the loss tangent, a very weak peak at a low temperature (--170 K) and a rather strong one at a high temperature (--240 K). The activation energy required for the high temperature relaxation was nearly equal to that obtained in Arrhenius plots of σ· T and 1/T. The temperature-dependence of ac conductivities corresponded well to that of loss tangent. The results are explained in terms of small polarons of O, 2p holes hopping between oxygen sites. The reorientation of holes bound to Li
+ ions gives rise to the low temperature relaxation. A theoretical calculation provides a direct evidence for stability of small polarons of O, 2p holes in CoO.
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Tatsuya Okada, Takahide Satoh, Masayuki Matsumura, Satoru Ono
Subject area: Electronic transport in condensed matter.
1996 Volume 65 Issue 1 Pages
230-236
Published: January 01, 1996
Released on J-STAGE: October 01, 1999
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The conductivities of liquid Ge
1-cSe
c alloys on the Ge-rich side decrease monotonically with increasing Se composition. The composition dependence of conductivity at 1023K exhibits a broad minimum at the composition c=0.72. The composition dependence of thermopower exhibits a maximum and a minimum with positive values at the compositions c=0.55 and 0.6, respectively. The addition of Se to liquid GeSe
2 gives rise to an abrupt increase in thermopower. The electrical behaviour of liquid Ge
1-cSe
c alloys with c≤0.3 was understood from the decrease in the conduction electrons due to the formation of chemical bonds. The conductivity and thermopower near the stoichiometric GeSe and GeSe
2 were analyzed by assuming an energy-dependent conductivity. The conductivity gap at 1023K varies widely from about 0eV for liquid GeSe to about 1.4eV for liquid GeSe
2.
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Keiichi Ikegami, Shin–ichi Kuroda, Hiroaki Tachibana, Mutsuyoshi ...
Subject area: Electronic structure and electrical properties of surfaces, interfaces and thin films.
1996 Volume 65 Issue 1 Pages
237-245
Published: January 01, 1996
Released on J-STAGE: October 01, 1999
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Langmuir-Blodgett films of several 1:2 charge-transfer complexes of azobenzene-containing alkylpyridinium and tetracyanoquinodimethane (TCNQ), which exhibit various conductivity-change phenomena upon UV and visible light irradiation, have been investigated by using the ESR technique. The in-situ illumination measurements of these films and the quantitative analyses of the obtained spectrum show the changes in the exchange couplings between the spins and suggest the structural change in the TCNQ columns. By adopting the one-dimensional Hubbard model with dimerization effect, we propose a conductivity-change mechanism in the system.
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Yoji Ohashi, Satoshi Takada
Subject area: Superconductivity.
1996 Volume 65 Issue 1 Pages
246-254
Published: January 01, 1996
Released on J-STAGE: October 01, 1999
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Condition for the mid gap state to exist in inhomogeneous superconductor is investigated. On the basis of the Andreev equations, a general expression of the wavefunction of this bound state is derived. Then, the mid gap state is shown to exist only if signs of the pair potential is different, which an quasiparticle feels in the initial and final states in the scattering process described by the Andreev equations. It is also studied why some inhomogeneous systems have no mid gap state. Our results present a unified picture that the absence of the mid gap states results from their hybridization due to the spatial variation of the order parameter and the presence of the normal reflection.
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Ludwik Dobrzynski, Robert J. Papoular, Makoto Sakata
Subject area: Magnetic properties and materials.
1996 Volume 65 Issue 1 Pages
255-263
Published: January 01, 1996
Released on J-STAGE: October 01, 1999
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We have reanalysed the polarized neutron data for the magnetic form factors of Fe (Shull and Yamada, 1962) and Ni (Mook, 1966, Maniawski et al., 1981) using the model-free Maximum Entropy technique. The magnetic anisotropy of e
g and t
2g types, respectively, is clearly visible. An apparently new feature observed is a depletion of the magnetization density at nuclei positions. One can prove that its observation was possible because of an enhanced spatial resolution of the MaxEnt method. From a model-free MaxEnt point of view, effect of a presence of the negative magnetization is of the order of the sensitivity of MaxEnt. The data can be fitted almost equally well by a strictly positive or a positive/negative magnetization distribution, which agrees with conclusions of Dobrzynski (1976) and Kaprzyk et al. (1981). If presence of the negative magnetization is assumed, the corresponding form factors give contribution to the innermost reflections and vary in an oscillatory manner.
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Yoshiyuki Fukumoto, Akihide Oguchi
Subject area: Magnetic properties and materials.
1996 Volume 65 Issue 1 Pages
264-272
Published: January 01, 1996
Released on J-STAGE: October 01, 1999
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The magnetic susceptibility of the XXZ model is studied over a wide temperature range by the Green's function method with the Kondo-Yamaji decoupling scheme. By this method it is possible that both XY- and Ising-like systems are studied in a unified way. In the XY-like system, our results of the transverse uniform susceptibility agree with those of a Monte-Carlo simulation. In the Ising-like system, our temperature dependence of the longitudinal uniform susceptibility agrees well with the experimental results of the susceptibility of quasi-2D Ising-like antiferromagnet K
2CoF
4 above its Néel point.
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Masashi Hase, Yoshitaka Sasago, Ichiro Terasaki, Kunimitsu Uchinokura, ...
Subject area: Magnetic properties and materials.
1996 Volume 65 Issue 1 Pages
273-279
Published: January 01, 1996
Released on J-STAGE: October 01, 1999
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Magnetizations of spin-Peierls cuprates Cu
1-xZn
xGeO
3 with x=0, 0.005, 0.010, and 0.020 were measured in order to investigate influence of impurities on a magnetic phase. A characteristic change of the magnetization related to a phase transition from dimerized to other phases was seen below a spin-Peierls-transition temperature. The magnetization above 16.0 T shows weak x and temperature dependences. A critical field associated with the phase transition decreases with increasing x. We derived a result that the effects of impurities on the magnetic phase are weaker than on the dimerized phase.
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Sanshiro Sako, Yoshifumi Umemura, Kazunari Ohshima, Masahiro Sakai, Sh ...
Subject area: Magnetic properties and materials.
1996 Volume 65 Issue 1 Pages
280-284
Published: January 01, 1996
Released on J-STAGE: October 01, 1999
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Superparamagnetism was observed in antiferromagnetic MnO ultrafine-particles with the size range of 3.7-- 5.4, nm. The decrease of Néel temperature in these finite systems was confirmed by measuring the temperature dependence of the magnetic susceptibility. The size dependence of a magnetic moment per atom and per particle was estimated by fitting the magnetic susceptibility to the Curie-Weiss law at higher and lower temperature than the Néel temperature, respectively. The former increased with decreasing size due to the surface effect, and the latter increased in proportion to the square root of the number of spins in a particle as expected in antiferromagnetic particles. The size dependence of the coercive force and the blocking temperature was remarkable in this narrow size range due to the magnetic interaction between particles.
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Koji Akai
Subject area: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
1996 Volume 65 Issue 1 Pages
285-292
Published: January 01, 1996
Released on J-STAGE: October 01, 1999
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Nuclear spin-lattice relaxation rate T
1-1 is calculated near the nuclear magnetic phase transition by the high temperature expansion method up to the order of 1/T in metallic nuclear magnets.T
1-1 deviates from the Korringa law in the vicinity of the critical temperature T
c for nuclear magnetism due to the growing short range order.For the nuclear spins interacting with the nearest neighbor spins, it is shown that the first order correction to the Korringa law, which is of the order of T
0, acts to reduce or enhance T
1-1 depending on the crystal structure.The next order correction of the order of 1/T acts to reduce T
1-1, irrespective of the sign of interaction and the lattice structure.The amount of the correction is larger in the Ising model than in the Heisenberg model, that is, the quantum spin fluctuation tends to suppress the deviation.
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Takeshi Moriya, Hiroyuki Nakashima, Yuichirõ Isokane, Toru Miya ...
Subject area: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
1996 Volume 65 Issue 1 Pages
293-296
Published: January 01, 1996
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Mössbauer effects are observed to study phase separation process in the Fe--Co--Al alloy system from the as-quenched state to the A2+B2 phases. The Al-rich and Al-poor sides of the phase boundary and the tie-lines are accurately determined. We analyze a Mössbauer spectrum decomposing it into subspectra corresponding to iron atoms under varieties of environments, supplemented by empirical relations between hyperfine field parameters and the occupation numbers of the nearest neighboring atoms. The results are compared with those by Ackermann (Thesis, Universität Dortmund, 1988) who also studied the same system by Mössbauer analysis, obtaining the distribution of the internal field by the method of Window (J. Phys. E, Sci. Instrum. 4 (1971) 401).
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Shojiro Kimura, Hitoshi Ohta, Mitsuhiro Motokawa
Subject area: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
1996 Volume 65 Issue 1 Pages
297-303
Published: January 01, 1996
Released on J-STAGE: October 01, 1999
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Antiferromagnetic resonances (AFMR) and EPR of R
2Cu
2O
5 (R=Y, Lu, In) powders have been observed from 1.8K to 265K by submillimeter wave ESR in the frequency region 90 to 383GHz using pulsed magnetic field up to 16T. The frequency field relations below T
N turned out to be quite different among above materials. AFMR modes have been analyzed by the model which was used previously to interpret the two successive metamagnetic transitions observed in the magnetization process of R
2Cu
2O
5.
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Yong–Hae Kim, Bog–Gi Kim, Jong–Jean Kim
Subject area: Dielectric properties and materials.
1996 Volume 65 Issue 1 Pages
304-306
Published: January 01, 1996
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Dielectric anomalies were observed in ammonium sulfate [(NH
4)
2SO
4] crystals at T
0≅ 413K after the crystal was heated above 413K. Frequency dependence of dielectric loss across T
0≅ 413K observed in the 2nd heating-up cycle could be best fitted by two overlapping relaxation functions of the Cole-Cole type. The fast component in higher frequency region depicts a sharp discontinuity of relaxation frequency at T
0≅ 413K while the slow component in lower frequency region shows a continuous slowing down to zero relaxation frequency as temperature increased to T
0≅ 413K.
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