Journal of the Physical Society of Japan
Online ISSN : 1347-4073
Print ISSN : 0031-9015
ISSN-L : 0031-9015
Volume 66, Issue 5
Displaying 1-50 of 58 articles from this issue
  • Shinsuke Watanabe, Mayumi Kawaguchi, Katsuyuki Kawamura, Shingo Ishiwa ...
    Subject area: Mathematical methods in physics.
    1997 Volume 66 Issue 5 Pages 1231-1233
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    A shock wave in a nonlinear LC circuit with dissipation has been investigated theoretically and experimentally. A shock wave solution of a stationary waveform traveling with a constant velocity and a higher-order correction have been obtained theoretically. In the experiment, it has been demonstrated that a shock wave with a constant amplitude propagates stably in a nonlinear LC circuit with dissipation. The velocity and width of the shock wave have been observed to be consistent with the theoretical prediction, provided that the amplitude is small enough to be consistent with the theoretical approximation.
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  • Ken Sekimoto
    Subject area: Statistical physics and thermodynamics.
    1997 Volume 66 Issue 5 Pages 1234-1237
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    Langevin equations have been employed to describe thermally fluctuating systems, such as thermal ratchet models.Their role of the heat bath in these contexts has not been clearly understood.We introduce an approach to this issue and, by using it, propose a method to study the energetics of those models. As a example, we calculate the efficiency of energy conversion of ''Feynman's ratchet''.
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  • B. H. Wang, P. M. Hui
    Subject area: Statistical physics and thermodynamics.
    1997 Volume 66 Issue 5 Pages 1238-1241
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    A microscopic approach to one-dimensional (1D) cellular automaton trafficflow models is presented. Starting from an equation describing the timeevolution of the Boolean variable, which describes whether a site isoccupied by a car or empty, defined on each site and using adecoupling approximation, an equation relating the average speeds v(t+1)and v(t) is obtained. This relation can be treated as a dynamicalmapping between the average speeds v(t+1) and v(t).The average speed in the long time limit can be obtained by studying theattractors of the mapping and their stabilities. The approach is alsoapplied to models with random delays. Results that are in agreement withsimulation data and previously proposed mean field theories using macroscopicconsiderations are obtained. Our approach thus represents a microscopicmethod of deriving mean field theories with the advantage that controllableapproximations can be introduced step by step.
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  • Susumu Shimomura, Toshiaki Fukui, Hikaru Terauchi
    Subject area: Equations of state, phase equilibria, and phase transitions.
    1997 Volume 66 Issue 5 Pages 1242-1244
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    X-ray diffraction studies of [N(CH3)4]2CuCl4 single crystals have been carried out under hydrostatic pressure at room temperature.With increasing pressure, phase transitions take place successively, to a monoclinic phase with a unique axis along b (space group, C2h5-P121/c1) at 1.4 GPa, to a monoclinic phase with a unique axis along c (C2h5-P1121/n) at 1.7 GPa, and then to an orthorhombic phase (D24-P212121) at 3.4 GPa. The transition to the highest-pressure phase is accompanied by a discontinuous change in the crystal color from light yellow to dark green. The color change is considered to be a result of a change in CuCl42- anion geometry.
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  • Tamifusa Matsuura, Atsushi Tsuruta, Yoshiaki Ono, Yoshihiro Kuroda
    Subject area: Electron states in condensed matter.
    1997 Volume 66 Issue 5 Pages 1245-1248
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    Infrared divergence in the pseudo-particle spectra of the degenerate impurity Anderson model described in terms of the auxiliary particles is examined rigorously with use of the expansion from the large limit of the spin-orbital degeneracy N. The results of analysis with the most divergent terms in the expansion confirm the exponents of the spectra of the slave boson and the pseudo-fermion to be given respectively by 1-nf2/N and (2n_f-nf2)/N where n_f is the average number of localized electrons at the impurity site, rather than by N/(N+1) and 1/(N+1) as suggested by the results of so-called non-crossing approximation (NCA) studies. In determination of the correct exponents, contributions from the crossing diagrams are crucial. It is also confirmed that all of the infrared divergences in the single particle spectra are cancelled out by the corresponding vertex corrections to leave only non-divergent terms in the scattering rate of the conduction electrons.
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  • Hitoshi Seo, Hidetoshi Fukuyama
    Subject area: Electron states in condensed matter.
    1997 Volume 66 Issue 5 Pages 1249-1252
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    The magnetic structure of antiferromagnetically ordered phases of quasi-one-dimensionalorganic conductors is studied theoretically at absolute zerobased on the mean field approximation to the quarter-filled band with on-site and nearest-neighbor Coulomb interaction.The differences in magnetic properties between the antiferromagnetic phase of (TMTTF)2Xand the spin density wave phase in (TMTSF)2X are seen to be due to a varying degrees of roles played by the on-site Coulomb interaction.The nearest-neighbor Coulomb interaction introduces chargedisproportionation, which has the same spatial periodicity as the Wigner crystal, accompanied by a modified antiferromagnetic phase.This is in accordance with the results of experiments by Nakamura et al on (TMTTF)2Br and (TMTTF)2SCN.Moreover, the antiferromagnetic phase of (DI-DCNQI)2Ag is predictedto have a similar antiferromagnetic spin structure.
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  • Eiji Hashimoto, Yoshitake Ueda, Hitoshi Yamasaki
    Subject area: Electronic transport in condensed matter.
    1997 Volume 66 Issue 5 Pages 1253-1256
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    Measurements have been made on the anisotropic dependence of the bulkresidual resistivity ρb at 4.2, K on the current direction inAl single crystals with a {110} main surface. In specimens with RRR≅10000, the anisotropy of ρb is relativelyweak, but shows a fine structure that corresponds to the detailed structureof the Fermi surface of Al: ρb rises nearly in the directionin which the Fermi surface intersects the Brillouin zone boundary. As thepurity level of the specimens increases, the degree of anisotropy increasesmarkedly and the behavior of its own changes. In specimens with{RRR}~=100000, ρb increases monotonically in theorder of the [110], [111] and [001] directions: the values along [001] and[111] are about 75 and 30, In the [001] direction, the second-zone Fermi surface is nearest to thezone boundary.
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  • Keizo Endo, Hiroko Matsuda, Kiyoshi Ooiwa, Masanori Iijima, Kazuo Ito, ...
    Subject area: Electronic transport in condensed matter.
    1997 Volume 66 Issue 5 Pages 1257-1260
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    Electrical resistance, magnetoresistance and magnetization were measured for Heusler-type alloys, Fe2+xV1-xGa. An anomalous giant magnetoresistance (GMR) near 50\inhomogeneous ferromagnet. For alloys with x>0, which show clear ferromagnetism, the electrical resistance showed an anomaly below the Curie temperature. For alloys with x<0, the temperature dependence of the resistance indicated behavior like that of a semiconductor. The energy gap was tentatively estimated to be 0.03, eV for x=-0.10. The origin of the present GMR is discussed in terms of the metal-insulator transition arising from ordering of the magnetic moment.
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  • Keiji Ono, Hiroshi Shimada, Youiti Ootuka
    Subject area: Electronic structure and electrical properties of surfaces, interfaces and thin films.
    1997 Volume 66 Issue 5 Pages 1261-1264
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    We report on magnetotransport properties of a ferromagnetic single electron transistor (SET) in which tunnel resistance RmT changes about 3.6-3.8% by the magnetic valve effect. We find that the magnetic valve effect is enhanced in the Coulomb blockade region: The magnetoresistance (MR) ratio of the off-state of the SET is more than 40%, while that of the on-state is 4.0%. A mechanism of enhancement by the higher-order tunneling process is proposed. Furthermore, we find a monotonic phase shift of the Coulomb oscillations induced by the magnetic field, which results in magneto-Coulomb oscillations with fixed gate voltage. A simple explanation for this effect based on a magnetic-field-induced change in the Fermi energy of the spin-polarized electrons in an island electrode is given.
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  • Masakazu Ito, Hideto Yamashita, Tatsuya Kawae, Kazuyoshi Takeda
    Subject area: Magnetic properties and materials.
    1997 Volume 66 Issue 5 Pages 1265-1267
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    Heat capacity measurement has been carried out on the Haldane system NENP under the pressure P between 0 kbar-5bar-1, where γ corresponds to the magnetic Grüneisen constant and κ_b to the compressibility along the chain axis of the NENP. No trace of three-dimensional ordering is detected in the present pressure and temperature ranges.The amplitude of magnetic heat capacity is not constant and increases roughly with increasing pressure. This behavior is considered to be due to the pressure dependence of single ion anisotropy D and interchain exchange interaction J'.
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  • Kwang–Sei Lee, Jong–Ho Park, Kum–Bae Kim, Jeong&ndas ...
    Subject area: Dielectric properties and materials.
    1997 Volume 66 Issue 5 Pages 1268-1271
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    The dielectric constant of TlH2PO4 along the b axis, ε b, was measured as a function of temperature between 290 and 443, K. The ε b displayed a new high-temperature anomaly at about 425, K (TP) on heating above the ferroelastic-paraelastic transition at 356, K (TU), while it showed a quasi-irreversibility on subsequent cooling to room temperature. After prolonged heat treatment at and above TP, microscopic spots, which grew into multigrains, were observed, indicating an additional tendency towards the incipient partial decomposition at temperatures above TP. The appearance of spots and the persistence of the high-temperature state on cooling back to room temperature suggest that the high-temperature anomaly near TP is topochemical in nature and that polymerization due to dehydration can take place on tempering near TP. The quasi-irreversibility of ε b seems to result from the nonstoichiometry at the surface.
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  • Kikuo Harigaya
    Subject area: Optical properties and condensedmatter spectroscopy and other interactions of matter with particles and radiation.
    1997 Volume 66 Issue 5 Pages 1272-1275
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    The component of photoexcited states with large spatial extent is investigated for poly(para-phenylenevinylene) using the intermediate exciton theory. We find a peak due to long-range excitons at the higher-energy side of the lowest main feature of optical spectra. The fact that the onset of long-range excitons is located near the energy gap is related to the mechanisms of large photocurrents measured in such energy regions. We show that a large value of thehopping integral is realistic for characterizing optical excitations.
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  • Roberto A. Kraenkel, Miguel A. Manna, Juan C. Montero, José G. ...
    Subject area: Mathematical methods in physics.
    1997 Volume 66 Issue 5 Pages 1277-1281
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    We apply a multiple-time version of the reductive perturbation method to study long waves as governed by the shallow water wave model equation. As a consequence of the requirement of a secularity-free perturbation theory, we show that the well known N-soliton dynamics of the shallow water wave equation, in the particular case of α =2β, can be reduced to the N-soliton solution that satisfies simultaneously all equations of the Korteweg-de Vries hierarchy.
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  • Kwok W. Chow
    Subject area: Mathematical methods in physics.
    1997 Volume 66 Issue 5 Pages 1282-1287
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    `Dromions' are exact, localized solutions of higher dimensional evolution equations decaying exponentially in all directions. They travel along tracks provided by the solitons of the auxiliary fields. When the solitons exhibit resonance the status of the dromions will be in doubt. This phenomenon is investigated by two well known model evolution equations. Possible results include a drastic attenuation in amplitude and a mode transformation.
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  • Thangavel Alagesan, Ambigapathy Uthayakumar, Kuppusamy Porsezian
    Subject area: Mathematical methods in physics.
    1997 Volume 66 Issue 5 Pages 1288-1290
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    In this paper, the generalisation of integrable (2+1)-dimensional dispersive long-wave equation (GDLWE) introduced by Boiti et al. is considered and is shown to possess the Painlevé (P-) property. The bilinear transformation is obtained straightforwardly from the Painlevé analysis.
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  • Rei Inoue, Miki Wadati
    Subject area: Mathematical methods in physics.
    1997 Volume 66 Issue 5 Pages 1291-1293
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    A new hierarchy of integrable nonlinear differential-difference equations is reported. Through an extension of the Miura transformation, such a series of discrete models are obtained from the hungry Volterra model. In addition, the relation to the lattice W-algebra is discussed.
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  • Masahiko Yoshioka, Masatoshi Shiino
    Subject area: Statistical physics and thermodynamics.
    1997 Volume 66 Issue 5 Pages 1294-1305
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    Associative memory of analog neural networks for which the concept of energy functions is lost is studied by means of the SCSNA (Self-Consistent Signal-to-Noise Analysis).Asymmetric synaptic couplings with biased random patterns are assumed together with positive-valued transfer functions which allow nonmonotonicity resulting from an appropriate cut off of output activity. Phase diagrams are given in terms of several parameters of the networks, showing the occurrence of enhancement of the storage capacity due to nonmonotonic transfer functions. Super retrieval states ensuring errorless memory retrieval under the loading of extensively many patterns are allowed to remain in existence in the presence of asymmetric synaptic couplings with biased patterns. A sample-dependent component in the local fields of neurons, which arises from the assumed asymmetric couplings, is discussed and shown to become of no effect in the super retrieval phase.
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  • Norio Inui, Makoto Katori, Genichi Komatsu, Koichi Kameoka
    Subject area: Statistical physics and thermodynamics.
    1997 Volume 66 Issue 5 Pages 1306-1309
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    We consider a quantity, αn, m= the number of directed compact site animals with m sites at the height n. We give an explicit expression for αn, m and calculate the mean width and the variance ofwidth at the height n of directed compact animals exactly. The number of αn, m is identified with a coefficient appearing in the series expansion for the directed site percolation.An extrapolation formula of directed site percolation probability for the square lattice is obtained usingthis number. The generating function of αn, m is calculated and some summation formulae are given.
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  • Toru Kinugawa, Katsumi Sakurai
    Subject area: Molecular spectra and interactions of molecules with photons.
    1997 Volume 66 Issue 5 Pages 1310-1320
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    For intuitive as well as quantitative understanding of femto-second molecular phototransitions, which are experimentally realized by ultrashort pulse laser, we have developed a convenient classical trajectory method: semiclassical Monte Carlo path integration based on the real-time propagator of Van Vleck and Gutzwiller. By combining this semiclassical propagator with the perturbation theory of the light-molecule interaction, we have obtained a semiclassical path-integral formalism of the real-time molecular phototransitions based on the semiclassical Franck-Condon condition. The present computational scheme consists of the Monte Carlo samplings of the initial values, subsequently the classical trajectory computations, the quantum jump to another potential surface and the final superposition of the semiclassical amplitudes. Numerical tests were done successfully for a one-dimensional realistic sample, i.e., the real-time photoexcitation of I2X1Σ +g⇔ B 3Π0+u. For multi-dimensional applications, we briefly mention a positive prospect by demonstrating a semiclassical quantization of weak chaos.
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  • Michisato Toyoda, Masahiro Kimura, Takekiyo Matsuo
    Subject area: Experimentally derived information on atoms and molecules: instrumentation and techniques.
    1997 Volume 66 Issue 5 Pages 1321-1323
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    We have demonstrated the existence of metastable excited rhodamine molecular ions when created in laser desorption ionization.Rhodamine ions were stored in a rf ion trap, and photodissociation was used to probe the metastable population as a functionof trapping time. From the dependence of the population decayon buffer gas pressure and by extrapolating it to zero pressurewe have obtained the lifetime of the metastable state of the ions in isolated condition.
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  • Yoko Kato, Noriko Koide, Masatomo Sato
    Subject area: Fluid dynamics.
    1997 Volume 66 Issue 5 Pages 1324-1330
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    An analytic solution of the Charney-Hasegawa-Mima equaiton, a two-dimensional nonlinear equation describing geostrophic Rossby flow and plasma drift flow, is given which represents a stationary vortex of an elliptic boundary in a background flow having a linear shear. The solution is obtained through an appropriate ansatz for the arbitrary function of integration of the stationary equation. Three types of vortices emerge according to the chioce of parameters which characterize the distribution of vorticity: a generally asymmetric dipole inside the boundary ellipse E, a monopole inside E, and a larger dipole lying across E.
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  • Hideaki Miura, Shigeo Kida
    Subject area: Fluid dynamics.
    1997 Volume 66 Issue 5 Pages 1331-1334
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    A new method is proposed to extract the axes of tubular vorticesin turbulence.Loci of sectional local minimum of the pressure associated with theadvection acceleration are traced numerically.It is applied to a homogeneous isotropic turbulence to demonstrate that swirling motions actually exist around these axes.The present method is shown to be superior to several typical onescommonly used in identifying tubular vortices.
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  • Hiroshi Amemiya
    Subject area: Kinetic and transport theory of fluids; physical properties of gases.
    1997 Volume 66 Issue 5 Pages 1335-1338
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    The criterion for the formation of a stable positive ion sheath is calculated for an arbitrary electron velocity distribution function to obtain the ion flux. The cases of Maxwellian and Druyvesteyn distributions are discussed for comparison. A diagnostic method for the positive ion density from the measured kinetic energy distribution by using the positive ion current region in the probe characteristic is suggested. The ion current density extractable from an ion source can also be estimated. Examples based upon experimental data are given to study the effect of non-Maxwellian velocity distribution.
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  • Yukinobu Kawakita, Makoto Yao, Hirohisa Endo
    Subject area: Structure of liquids and solids; crystallography.
    1997 Volume 66 Issue 5 Pages 1339-1350
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    The measurements of electrical conductivity σ, density, EXAFS and neutron scattering were carried out for liquid K--Te and Rb--Te mixtures. The conductivity σ decreases rapidly with alkali concentration and a metal-semiconductor transition occurs at about 10, at.\ early independent of the alkali species. The Te--Te bond length deduced from EXAFS and neutron scattering measurements is 2.8, Å and changes little with alkali concentrations. The average distances from K and Rb atom to Te atoms are 3.6, Å and 3.8, Å, respectively. Two kinds of relaxation processes are observed in quasielastic neutron scattering for K20Te80. Upon the addition of alkali the interaction between the neighbouring Te chains, which is responsible for the metallic conduction, weaken considerably.
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  • Victoria A. Shuvaeva, Koichiro Yanagi, Kiyoshi Sakaue, Hikaru Terauchi
    Subject area: Structure of liquids and solids; crystallography.
    1997 Volume 66 Issue 5 Pages 1351-1355
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    Nb positions in KNbO3 crystal were determined at room temperature via polarized Nb K-XAFS measurements. It has been revealed that the direction of Nb displacement in orthorhombic phase is very close to polar axis direction. This refute eight-site model which assumes that Nb atoms are disordered among several equivalent positions and phase transition are of order-disorder type. Analysis of polarized XAFS data showed that only slight disorder among close positions is possible. The distance between these positions is of an order of temperature atomic displacements, so the disorder, if any, is likely of dynamic nature. Results obtained are in perfect agreement with X-ray diffraction data.
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  • Huang Shi Ping, Fukuo Yoshida
    Subject area: Structure of liquids and solids; crystallography.
    1997 Volume 66 Issue 5 Pages 1356-1359
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    Dynamical properties of ions are studied in the metal-salt solution Cax(CaCl2)1-x. The concentration dependence of velocity autocorrelation functions and characteristic frequencies are discussed by comparing with molecular dynamics calculations.
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  • Tomoyuki Asari, Tsutomu Sato
    Subject area: Lattice dynamics and crystal statistics.
    1997 Volume 66 Issue 5 Pages 1360-1363
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    We measured the first-order Raman band of A1g mode of SnO2 crystal in the temperature range from 300 to 973, K. The results of the frequency shift and the band width were found to be agree well with the calculated results taking the thermal expansion into account. It is confirmed that the frequency shift and the band width can be explained unifiably by the phonon self-energy considering the thermal expansion.
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  • Tomoko Imasaka, Shoji Hirokawa
    Subject area: Equations of state, phase equilibria, and phase transitions.
    1997 Volume 66 Issue 5 Pages 1364-1370
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    The orientational ordering in a system of dipolar molecules located on a trigonal lattice is studied in the eight-sublattices approximation. Our concrete example is SO2 molecules enclosed in β-hydroquinone clathrate. It is assumed that the molecules interact with each other via effective dipole-dipole interactions, and that the crystal field acting on those molecules is of the form WA=Ccos[ ν ( φ - δA ) ], where φ is a rotational angle and A is a sublattice number. If ν is an odd integer, we assume that δA may be different for different A. The mean electric field which depends on the depolarization field is obtained. Various cases of C, ν, δA are investigated. Results are as follows: the possible dipole arrangement is antiferroelectric in all cases; the phase transition for ν=2, 4, 5, 6 is of second order; if ν = 1, no disordered phase occurs; if ν = 3, the phase transition is weakly of first order except for special cases; the C dependence of the transition temperature is weak unless ν = 2; δA chiefly determines the equilibrium direction. A comparison with experiment suggests that the low-temperature phase of SO2-β-hydroquinone has ν = 2 or 3, and that interactions between enclosed SO2 molecules other than dipole-dipole interactions may be also effective.
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  • Manabu Kiguchi, Toshihiko Yokoyama, Yuichi Okamoto, Toshiaki Ohta, Har ...
    Subject area: Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties).
    1997 Volume 66 Issue 5 Pages 1371-1377
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    The vibrational anisotropy and anharmonicity of the surface adsorbate-substrate bonds in c(2× 2)S and Cl/Ni(100) systems were investigated by means of classical molecular dynamics calculations. The obtained results were compared to those experimentally given by surface extended X-ray absorption fine structure and high-resolution electron energy loss spectroscopies. Good agreement between calculated and experimental results indicates high reliability of the present method. The calculations allow us to distinguish the component of motions parallel to the surface from the normal one. In both systems, the mean-square displacements of the adsorbates were found to be noticeably greater in the normal direction than in the lateral one. On the other hand, it was revealed that the mean-square relative displacement concerning the S--Ni pair is enhanced in the vertical direction, while that of the Cl--Ni one shows less directional dependence. Such a difference can simply be understood from the local surface geometries.
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  • Yoshiya Homma, Masaoki Oku, Kenji Sumiyama, Takehiko Hihara, Hitoshi A ...
    Subject area: Electron states in condensed matter.
    1997 Volume 66 Issue 5 Pages 1378-1386
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    Valence band and core level XPS spectra have been measured for the amorphous CexRu100-x (x=18, 58, 81), CexCu100-x (x=14, 33, 50) and Ce66Si34 alloys produced by sputtering. The coupling constant between the 4f and conduction electron levels, Δ, and the number of 4f electrons, nf, are estimated from the Ce-3d core level spectra. The amorphous CexCu100-x (x=14, 33, 50) and Ce66Si34 alloys are heavy fermion systems with small Δ, while the amorphous CexRu100-x (x=18, 58, 81) alloys are intermediate valence systems with large Δ. We also derive the zero temperature magnetic susceptibility, χ (0), and Kondo temperature, TK, from these spectroscopic data and compare with those estimated from several low temperature physical properties.
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  • Komajiro Niizeki, Eigo Yagi
    Subject area: Electron states in condensed matter.
    1997 Volume 66 Issue 5 Pages 1387-1390
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    We investigate the localization properties of electronic wave functionsalong the normal of a layered system which is a random stacking of two typesof composite layers X and Y. It is shown that the energy spectrum ofthe system can have one or more channels of extended statesif i) X or Y has a repeated structure, ii) X and Y are symmetric, or iii) X and Y are the mirror images of each other. A similar effectis expected for the case of electromagnetic or acoustic wave.
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  • Hideo Hasegawa
    Subject area: Electron states in condensed matter.
    1997 Volume 66 Issue 5 Pages 1391-1397
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    A slave-boson functional-integral method has been developed forthe Hubbard model with arbitrary, orbital degeneracy D.Its saddle-point mean-field theory is equivalent to the Gutzwiller approximation, as in the case of single-band Hubbard model.Our theory is applied to the doubly degenerate (D=2) model, whose paramagnetic state has been studied by numerical calculations.The effect of the exchange interaction on the metal-insulator (MI)transition is discussed.The critical interaction for the MI transition is analytically calculated as functions of orbital degeneracy and electron occupancy.
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  • Shuntaro Yoda, Kosaku Yamada
    Subject area: Electron states in condensed matter.
    1997 Volume 66 Issue 5 Pages 1398-1404
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    We investigate the two-dimensional d-p model with use of the perturbation method for the half-filling. The self-energy is evaluated up to the second order with respect to the on-site Coulomb interaction U with the full momentum dependence included. Varying the transfer integrals, namely, the band width W, the one-particle spectra are calculated. We obtain the three-peak structure and the transfer of the spectral weight, which well correspond to experiments. However, the experimentally obtained small-mk behavior cannot be explained in our framework with only the on-site Coulomb interaction. The charge susceptibility is also calculated with the conserving approximation. The charge susceptibility is suppressed with increasing U/W. These results suggest the importance of the long-range Coulomb interaction near the Mott transition.
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  • Yoshiteru Maeno, Koji Yoshida, Hiroaki Hashimoto, Shuji Nishizaki, Shi ...
    Subject area: Electron states in condensed matter.
    1997 Volume 66 Issue 5 Pages 1405-1408
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    We report detailed normal state measurements of the resistivity, magnetic susceptibility and specific heat of high-quality single crystals of Sr2RuO4, the only copper-free, layered perovskite superconductor (Tc ≈ 1, K). It is intriguing that despite its very strong anisotropy (the ratio of the interlayer to in-plane resistivity exceeds 500) arising from the essentially two-dimensional Fermi surface, the normal state properties are consistent with a universal description for a strongly correlated Fermi liquid. Therefore, Sr2RuO4 serves as an ideal reference material for the investigation of the limits of applicability of Fermi liquid theory to other highly correlated layered compounds, including high-Tc cuprates.
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  • Yoshihiro Shimazu, Tomohiro Yamagata, Seiichiro Ikehata, Shun–ic ...
    Subject area: Electronic transport in condensed matter.
    1997 Volume 66 Issue 5 Pages 1409-1418
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    We report measurements on a series of ultrasmall Al single tunnel junctions. The leads were made of either multiple junctions connected in various ways or high-resistance NiCr films. The effects of tunnel resistance and lead resistance were studied extensively for normal-metal junctions and Josephson junctions. The dependence of the Coulomb blockade in normal-metal junctions on those resistances was compared quantitatively with theories. The observed tunnel-resistance dependence in Josephson junctions was explained as a manifestation of the dissipative phase transition predicted by the theory. The effect of lead resistance in Josephson junctions was also studied.
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  • Michio Watanabe, Hiroshi Shimada, Shun–ichi Kobayashi, Youiti Oo ...
    Subject area: Electronic transport in condensed matter.
    1997 Volume 66 Issue 5 Pages 1419-1426
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    To study the superconductor-insulator (SI) transition in two-dimensional systems, we measured electrical resistance of Sn granular films with 24 nm grains over a temperature range from 9 K to 50 mK. A distinct SI transition was observed when the normal-conducting sheet resistance RN is increased, showing that neither flat tail nor quasi reentrance is the intrinsic effect in granular systems. If we define RN as the sheet resistance at 77 K, the critical sheet resistance Rc for the SI transition exists between 6.0 kΩ and 6.9 kΩ. For the samples which showed superconductivity at low temperatures, we analyzed the resistance based on the vortex Kosterlitz-Thouless (KT) transition. Evaluating from the extrapolation of KT transition temperature Tc→0, Rc is 6.4 kΩ, which is very close to RQ≡h/4e2.
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  • Akira Oguri
    Subject area: Electronic transport in condensed matter.
    1997 Volume 66 Issue 5 Pages 1427-1437
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    We study the conductance for the current through a finite interacting, possibly disordered region attached to two noninteracting leads within the Kubo formalismapplying the perturbation theory for the local Fermi liquid developed by Yamada & Yosida and by Shiba to this finite region. Assuming the validity of the perturbation expansion in the Coulomb interaction and the time reversal symmetry for the normal scattering potential in the finite region, we find that the contributions of the vertex correction to the dc conductance disappear at T=0 if the currents are measured in the leads.Consequently, the conductance is expressed as g=(2e2/h), |t(0)|2. Here t(0) isthe transmission coefficient for single-particle-like excitation at the Fermi energy and is introduced by using the Green's function. The results are generalized to a quasi-one-dimensional system with a number of scattering channels.
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  • Shigeru Koikegami, Satoshi Fujimoto, Kosaku Yamada
    Subject area: Superconductivity.
    1997 Volume 66 Issue 5 Pages 1438-1444
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    The dressed d-electron Green's function of the d-p modelis computed self-consistently based on the fluctuation-exchange approximation.Using this Green's function and assuming the dx2-y2 symmetry forthe momentum dependence of the gap function, we obtain the reasonable superconducting transition temperature Tc in the several cases where the d-(p-)hole number is close to the experimental value of La1.76Sr0.24CuO4 based on NMR/NQR analyses.Using this Green's function, we calculate the d-electron spin susceptibility, which has very sharp incommensurate peaksnear Tc for the low frequency as observed in neutron scattering data on La1.86Sr0.14CuO4.The quasi-particle excitation spectrum in the normal state near Tc is also obtained from this Green's function. The energy dispersion of quasi-particles near the Fermi level is almost flat around the (π/a, 0) point. This electronic structure is due to many-body effects, rather than beinginduced by band effects.
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  • Takeo Kato, Masatoshi Imada
    Subject area: Superconductivity.
    1997 Volume 66 Issue 5 Pages 1445-1449
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    We study a current-biased 0-π-0 Josephson junction made by high-Tc superconductors, theoretically. When a length of the π junction is large enough, this junction contains a vortex-antivortex pair at both ends of the π junction. Magnetic flux carried by the vortices is calculated using the sine-Gordon equation. The result shows that the magnetic flux of the vortices is suppressed to zero as the distance between the vortices is reduced. By applying an external current, the orientation of the vortices is reversed, and a voltage pulse is generated. The current needed for this transition and generated pulse energy are calculated. Macroscopic quantum tunneling (MQT) in this transition is also studied. The tunneling rate has been evaluated by an effective Hamiltonian with one degree of freedom.
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  • Takehiko Hihara, Kenji Sumiyama, Masaki Sakurai, Hideya Onodera, Kimio ...
    Subject area: Magnetic properties and materials.
    1997 Volume 66 Issue 5 Pages 1450-1456
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    Fe cluster dispersed Fe_XCu100-X granular films have been produced by a cluster beam (CB) technique. X-ray diffraction and XAFS measurements indicate that the structure of Fe clusters is b.c.c. for x>60, f.c.c. for x<20 and b.c.c.+f.c.c. for 20100-X granular films: Fe clusters are spin glass in the dilute Fe-f.c.c., antiferromagnetic in the Cu-rich f.c.c. and ferromagnetic in the Fe-rich b.c.c. region.
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  • Yoshiya Homma, Kenji Sumiyama, Hiroshi Yamauchi, Kenji Suzuki
    Subject area: Magnetic properties and materials.
    1997 Volume 66 Issue 5 Pages 1457-1464
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    The amorphous Ce--Ru alloys produced by the sputtering technique show the following distinct behaviors at low temperatures. The electronic specific heat coefficient rapidly increases below 5, K for Ce--19 and 42, at.\alloys with decreasing temperature, T, (a heavy fermion behavior). The electrical resistivity displays -log T dependence at T>40, K (an incoherent or impurity Kondo effect). It slightly decreases at T<30, K for Ce--19 and 42, at.\may originate from the strong mixing and correlation of 4f-electrons and conduction-electrons even in the random alloy system.
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  • Hiroshi Ido, Takashi Nishioka, Masaaki Kontani
    Subject area: Magnetic properties and materials.
    1997 Volume 66 Issue 5 Pages 1465-1471
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    To clarify the heavy fermion properties of Th2Zn17-type Ce2CuxAl17-x(6.75 ≤ x≤ 8.25), we have systematically measured the electrical resistivity including the magnetoresistance, the magnetic susceptibility and the specific heat. In the electrical resistivity measurement for x=8.0, no magnetic order was clearly observed down to 60 mK and the magnetic contribution to the specific heat, Cm/T, reached extremely large values of Cm/T=3.0 (at 0.7 K), 2.4 (at 0.8 K) and 1.7 J/K2mol-Ce (at 1.4 K) for x=8.0, 7.5 and 7.0, respectively.A T2 dependence of the electrical resistivity was also observed below 0.4 K for x=8.0 and below 0.6 K for x=7.0 and 7.5, indicating that Ce2CuxAl17-x is a coherent heavy fermion system. However, the possibility of the coexistence of short-range magnetic order resulting from the random distribution of Cu and Al could not be entirely excluded. We discuss the large Cm/T values at temperatures close to 0 K in terms of the x dependence of the Kondo temperature, TK, and also discuss the differences between the magnetic properties of heavy fermion compounds such as CeCu_6 and those of Ce2CuxAl17-x.
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  • Tatsuo Komori, Hajime Takayama
    Subject area: Magnetic properties and materials.
    1997 Volume 66 Issue 5 Pages 1472-1479
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    Non-exponential slow dynamics in the `Griffiths phase' of the three-dimensional (3D) ± J Ising spin-glass model is studied by means of Monte Carlo simulation. The distribution of relaxation times averaged over samples, {\bar P}(x) with x=lnτ, is calculated from spin auto-correlation functions simulated. It is found that {\bar P}(x) consists of two branches. The cross-over value between the branches, xc, diverges as T→ Tc, Tc being the spin-glass transition temperature. Therefore τc (=exc) is regarded as the critical relaxation time associated with the onset of the spin-glass order at Tc, and the branch of {\bar P}(x) at xc is interpreted due to the ordinary critical slowing down process ({critical dynamics}). The other branch at x>xc causes the unusual slow dynamics peculiar to spin glasses. Various aspects of {\bar P}(x) of this branch examined are consistent with the following picture; compact regions with less frustrations than the system as a whole are thermally fluctuating with very small frequencies, and independently of each others ({cluster dynamics}).
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  • Qing Feng Lu, Izuru Umehara, Yoshiya Adachi, Masato Endo, Kiyoo Sato
    Subject area: Magnetic properties and materials.
    1997 Volume 66 Issue 5 Pages 1480-1484
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    Magnetization curve, magnetic susceptibility and electrical resistivity were measured for Pr3Co single crystals. The magnetization curves at 1.5, K were measured in magnetic fields up to 7, T. Metamagnetic transitions were observed at 0.85, T along the a-axis and 6.4, T along the b-axis, respectively. From the magnetic susceptibility, the effective magnetic moment is deduced to be 3.59, μ B/Pr ion, which is in good agreement with the Pr3+ free ion value.
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  • Mikito Koga, Hiroyuki Shiba
    Subject area: Magnetic properties and materials.
    1997 Volume 66 Issue 5 Pages 1485-1494
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    The stability of the non-Fermi liquid (NFL) in Kondo effect is studied by considering the excited states of the 5f-electrons. First, in order to examine their effects in the strong correlation limit, the exchange model is derived for a tetragonal crystal field by restricting the localized states in f2 to a non-Kramers doublet and a singlet;all the states are taken into account for f1.The numerical renormalization group analysis for this model showsthat the singlet state in f2 and one of the excited states in f1 play animportant role to stabilize the Fermi liquid (FL) over the NFL.Second, the same problem is examined for the six-fold orbitally degenerate Anderson model by considering all the local excited states.The competition between FL and NFL sensitively depends on the Coulomb and Hund couplings, the orbital anisotropy and the hybridization term.The six-fold orbital degeneracy is also important to realize NFL; in fact a similar analysis on the four-fold orbitally degenerateAnderson model does not lead to NFL.
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  • Kazuko Zenmyo, Hidenori Kubo
    Subject area: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
    1997 Volume 66 Issue 5 Pages 1495-1502
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    Proton NMR measurements are carried out in both of the antiferromagnetic (AF) and oblique antiferromagnetic (OAF) phases in the random mixture Fe1-xCoxCl2· 2H2O with competing anisotropies. NMR spectra show that in the Fe-rich and Co-rich antiferromagnetic phases all of Fe and Co magnetic moments point parallel to their easy axes, the α -axis for FeCl2· 2H2O (Fe-type AF) and the b-axis for CoCl2· 2H2O (Co-type AF), respectively. Some part of Fe spins tilt from b-axis near the boundary concentration region between the Co-type AF and OAF phases. In the OAF phase, both α - and b-components of the moments order independently. Then Fe and Co moments tilt from their easy axes with larger magnitudes of magnetic moments than that in the antiferromagnetic phase. These tilting moments coexist with the moments which are parallel to either α - or b-axis.
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  • Tatsuya Nagata, Makoto Iwata, Hiroshi Orihara, Yoshihiro Ishibashi, Yu ...
    Subject area: Dielectric properties and materials.
    1997 Volume 66 Issue 5 Pages 1503-1507
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    Temperature dependences of the third-order nonlinear dielectric constant in the mixed crystals of Rb1-x(NH4)xH2PO4 with x=0.25, 0.3, 0.4, 0.5, 0.6 and 0.7 were measured in the temperature range between 4 and 50, K. It was observed that the nonlinear dielectric constant in these crystals increases near the glass transition point and it is strongly dispersive at low frequencies. It was found that the third-order nonlinear dielectric constant is proportional to the imaginary part of the linear dielectric constant when measured under changing temperature at a fixed frequency.
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  • Masaki Maeda, Maki Hattori, Akifumi Hotta, Ikuo Suzuki
    Subject area: Dielectric properties and materials.
    1997 Volume 66 Issue 5 Pages 1508-1511
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    Dielectric dispersion measurements have been performed on CH3NH3PbX3 (MAPbX3, X = Cl and Br) single crystals at frequencies between 50 Hz and 1 MHz. Significant dielectric dispersion was observed in the cubic and tetragonal II phases for MAPbCl3 and in the cubic, tetragonal I and tetragonal II phases for MAPbBr3. The apparent dielectric dispersion was attributed to the ionic conductivity in the crystals. The static bulk conductivity was expressed by the Arrhenius-type formula σ = (A/T) exp (-ΔE /kT ). The activation energies for the ionic conduction along [100] axis for each phase are estimated to be 0.13 eV (cubic phase) for MAPbCl3 and 0.132 eV (cubic phase) and 1.60 eV (tetragonal I phase) for MAPbBr3.
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  • Ryu Takayama, Osamu Sakai
    Subject area: Optical properties and condensedmatter spectroscopy and other interactions of matter with particles and radiation.
    1997 Volume 66 Issue 5 Pages 1512-1525
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    Excitation spectra of the extended impurity Anderson model thatincludes the intra-atomic d-f Coulomb screening are studiedbased on the numerical renormalization group method. The low-energy fixed point is usually classified as the local Fermi liquid state.There is a regime in which the single particle and the magnetic excitation spectra can be scaled by the effective Kondo temperature, TK, which is reduced due to the screening effect. In this regime, the optical conductivity spectrum shows the excitonic shift in the energy region of the f → d atomiclike transition, and the extreme increase of the intensity in the low-energy region comparable to TK. In the valence fluctuation regime, the coupled charge fluctuations of f and d electrons occur.
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  • Takao Nanba, Yasuhiro Nodake, Makoto Muneyasu, Gwyn. P. Williams, Shin ...
    Subject area: Optical properties and condensedmatter spectroscopy and other interactions of matter with particles and radiation.
    1997 Volume 66 Issue 5 Pages 1526-1531
    Published: May 01, 1997
    Released on J-STAGE: October 01, 1999
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    We present experimental evidence which shows that the critical pressure (Pc) of the structural phase transition in CdS microcrystals under pressure differs from that of the bulk state and also that its magnitude depends on the microcrystal size. Far-infrared transmission measurements on CdS microcrystals of various sizes were carried out at pressure up to 8.3, GPa at room temperature by using synchrotron light source. The surface phonon at around 268, cm-1 at P=0 (atmosphere pressure) showed a blue shift with pressure. With further increase in pressure, the surface phonon showed a sudden decrease in energy. The very broad absorption band was found at the high pressure phase after the structural phase transition. Particle with smaller diameters was found to show higher Pc values. The origin of the increase in the Pc value is discussed related to thermodynamics and a surface tension of microcrystal.
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