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M. T. Batchelor, V. Fridkin, Atsuo Kuniba, Kazumitsu Sakai, Y .– ...
Subject area: Statistical physics and thermodynamics.
1997 Volume 66 Issue 4 Pages
913-916
Published: April 01, 1997
Released on J-STAGE: October 01, 1999
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We obtain the free energies and critical exponents of modelsassociated with elliptic solutions of the star-triangle relation andreflection equation. The models considered are related to the affineLie algebras A
1(1), B
n(1), C
n(1) and D
n(1). Thebulk and surface specific heat exponents are seen to satisfy thescaling relation 2α
s = α
b + 2. It follows from scaling relations that in regime III the correlation length exponent ν is given by ν=(l+g)/2g, where l is the level and g is the dual Coxeter number. In regime II we find ν=(l+g)/2l.
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B. C. Chauhan, S. Dev
Subject area: Specific reactions and phenomenology.
1997 Volume 66 Issue 4 Pages
917-920
Published: April 01, 1997
Released on J-STAGE: October 01, 1999
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Recent solar neutrino data reveal a serious anomaly in the relative neutrino fluxes from different steps in the chain of thermonuclear reactions responsible for energy generation in the stars. Boron-8 neutrinos generated at the end of the chain are observed whereas hardly any Be-7 neutrinos generated at an intermediate stage of this chain are seen. This almost rules out an astrophysical solution of the solar neutrino puzzle. The only apparent way to save the whole logic of thermonuclear chain reactions occuring inside the stars is to invoke non-standard neutrino physics. In this work the Be/B neutrino flux anomaly has been examined within the framework of Resonant Spin Flavour Precession (RSFP) scenario. It is found that the survival probability for electronic neutrinos in the RSFP scenario has just the right dependence on neutrino energy to explain the Be-neutrino deficit for a suitable range of transverse solar magnetic field.
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Kazuya Uehara, Akira Tsushima, Hiroshi Amemiya, JFT–M Group
Subject area: The physics of plasmas and electric discharges.
1997 Volume 66 Issue 4 Pages
921-924
Published: April 01, 1997
Released on J-STAGE: October 01, 1999
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Simultaneous measurement of ion temperature and electron temperature as well as correlation with a H
α line and the ion behavior are performed by using a modified ion sensitive probe in the boundary plasma in the JFT-2M tokamak. The modified ion sensitive probe for the ion temperature measurement mounted in the JFT-2M can be used to vary the height of the electron barrier for suppressing the electron current by remote control without breaking of the vacuum. The electron temperature is simultaneously measured using the electron guard as a Langmuir probe while the ion temperature is measured by the ion collector of the probe. It has been confirmed that the ion temperature is higher than the electron temperature in the tokamak boundary plasma. It has also been found that the decrease of the ion current at the ion collector coincides with that of the H
α line intensity when the plasma confinement is improved during the divertor biasing.
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Hiroshi Furusawa, Kohzo Ito, Reinosuke Hayakawa
Subject area: Equations of state, phase equilibria, and phase transitions.
1997 Volume 66 Issue 4 Pages
925-928
Published: April 01, 1997
Released on J-STAGE: October 01, 1999
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The end-to-end vector distribution function of a semiflexible chain with an arbitrary persistence length is given in a simple analytical form. The explicit representation of the distribution function enables evaluation of the free energy of a highly charged network as a backbone of the gel where the electrostatic repulsive forces between charged groups increase not only the excluded volume but also the persistence length. The newly obtained free energy elucidates that the ionic swelling of highly charged gels is mainly due to the presence of the electrostatic persistence length unlike weakly charged ones where the electrostatic excluded volume effect plays an important role. This picture also explains the recently observed ionic dependence of the swelling degree and the elastic modulus.
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Satoru Miyashita, Yukio Saito, Makio Uwaha
Subject area: Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties).
1997 Volume 66 Issue 4 Pages
929-932
Published: April 01, 1997
Released on J-STAGE: October 01, 1999
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A dynamical scaling law of fractal aggregation is testedusing electrochemical deposition without an external electric field.Silver metal leaves grow on the edge of a Cu plate placed in a thin cell containing an AgNO
3-water solution due to the difference in ionization tendency between Ag and Cu. We find that the tip height h(t) satisfies the dynamical scaling relationh(t)= c^{-1/(d-D
f)} ˜{g}(tc^{2/(d-D
f)}) with respect to the solute concentration cin the space dimension d=2 with the fractal dimension D
f=1.71 of the diffusion-limited aggregation.
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Makoto Kuwabara, Shuji Abe, Yoshiyuki Ono
Subject area: Electron states in condensed matter.
1997 Volume 66 Issue 4 Pages
933-936
Published: April 01, 1997
Released on J-STAGE: October 01, 1999
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Interchain hopping of solitons and polarons in polyacetylene is studied by numerical simulation of their motion under an electric field. Use is made of the Su-Schrieffer-Heeger model supplemented with intrachain electron-electron interactions and dopant potentials. We find that charged solitons can hop to the opposite chain by forming bound pairs (bipolarons). For the case of polarons also, hopping in a pair is more favorable than single polaron hopping. Interchain hopping of a polaron pair is more efficient than that of a soliton pair.
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Yoshiaki Mizuno, Takami Tohyama, Sadamichi Maekawa
Subject area: Electron states in condensed matter.
1997 Volume 66 Issue 4 Pages
937-940
Published: April 29, 2007
Released on J-STAGE: October 01, 1999
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We examine the electronic states of Sr
14-xCa_xCu
24O
41 by the ionic and cluster model approach. It is found that self-doped holes are likely to stay on the chain at x=0 and Ca substitution drives the holes to move to the ladder. This feature is caused by changes of the positions of (Sr, Ca) layers, which results in enhancement of the electrostatic potentials in the chain. The optical conductivity is calculated with application of the exact diagonalization method to small Cu-O clusters. It is shown that the excitations below 2 eV are governed by the ladder, giving rise to the spectral weight transfer from the charge-transfer excitation at around 2 eV to low energy Drude excitation, while the contribution from the chain mainly emerges in a higher energy region showing large spectral weight at around 3 eV. These findings provide a consistent explanation for the results of a recent experiment.
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Hiroyuki Shiba, Ryousuke Shiina, Atsushi Takahashi
Subject area: Electron states in condensed matter.
1997 Volume 66 Issue 4 Pages
941-944
Published: April 01, 1997
Released on J-STAGE: October 01, 1999
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A possible origin is proposed on the anomalous optical absorption which is observed in ferromagnetic metal La
1-xSr
xMnO
3. It is argued that the interband transition within e
g orbitals is responsible for the absorption. The orbital dependence of transfer integrals is crucial to make the transition allowed.
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Hitoshi Ohkuni, Takashi Ishida, Yoshihiko Inada, Yoshinori Haga, Etsuj ...
Subject area: Electronic transport in condensed matter.
1997 Volume 66 Issue 4 Pages
945-948
Published: April 01, 1997
Released on J-STAGE: October 01, 1999
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We have measured the magnetoresistance and de Haas-van Alphen (dHvA) oscillation of URu
2Si
2. From the results of the magnetoresistance measurement, URu
2Si
2 is concluded to be a compensated metal with closed Fermi surfaces.The dHvA branch, which corresponds to a nearly spherical Fermi surface, has been detected in both the normal and superconducting mixed states. The Dingle temperature or the electron scattering rate is found to be strongly enhanced and the cyclotron effective mass to be correspondingly reduced in the mixed state.
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Takeshi Nakanishi, Tomi Ohtsuki, Toru Kawarabayashi
Subject area: Electronic transport in condensed matter.
1997 Volume 66 Issue 4 Pages
949-952
Published: April 01, 1997
Released on J-STAGE: October 01, 1999
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Diffusion of electrons in a two-dimensional system with time-dependentrandom potentials is investigated numerically.The correction to the conductivity due to inelastic scatteringsby oscillating potentials is shownto be a universal function of the frequency ω, which is consistent with the weak localization prediction\fracel{e^2}{3π^2 (h/2π)}log ω.
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Takayuki Nishio, Kenji Yonemitsu, Hiromichi Ebisawa
Subject area: Superconductivity.
1997 Volume 66 Issue 4 Pages
953-956
Published: April 01, 1997
Released on J-STAGE: October 01, 1999
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The quasi-particle spectrum for s-wave superconductors in the vortex-lattice state remains gapless in magnetic fields much below the upper critical field H
c2 where the cyclotron frequency is smaller than the amplitude of the pair potential.This is shown through self-consistent solutions of the Bogoliubov-de Gennes equations for the attractive Hubbard model on the square lattice.It has not been predicted in earlier theoretical works based on a continuous model because it is due to the dispersion of Landau subbands in the lattice model.
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Wataru Koshibae, Yuhki Kawamura, Sumio Ishihara, Satoshi Okamoto, Jun& ...
Subject area: Magnetic properties and materials.
1997 Volume 66 Issue 4 Pages
957-960
Published: April 01, 1997
Released on J-STAGE: October 01, 1999
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We present an exact diagonalization study for perovskite manganites using an effective Hamiltonian which includes a coupling between the spin and orbital degrees of freedomderived from a strong on-site Coulomb interaction and orbital degeneracy of Mn ions. We investigate spin and orbital orderings as well as their excitations for the undoped insulating and the doped charge-ordered phases using three-dimensional 2 × 2 × 2 clusters to maintain proper symmetry of the systems. It is shown that the anisotropic magnetic structures, such as A-type antiferromagnetic ordering, are realized by self-adjustment of the orbital ordering where the orbital degeneracy is lifted by spins, indicating a strong interplay of spins and orbitals.
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Nobuo Wada, Tatsuya Kobayashi, Hideo Yano, Tsunehisa Okuno, Akira Yama ...
Subject area: Magnetic properties and materials.
1997 Volume 66 Issue 4 Pages
961-964
Published: April 01, 1997
Released on J-STAGE: October 06, 2017
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Low temperature properties of the organic spin-1 Kagomé antiferromagnet, m-MPYNN·BF
4, have been studied by measuring heat capacity and magnetic susceptibility down to 35 mK. The heat capacity maximum due to a magnetic short-range order was observed at 1.4 K, which is about half of the antiferromagnetic interaction 2\lceilJ\
ceil/k
B=3.1 K in the Kagomé lattice. As temperature decreases, the susceptibility begins to decrease below 0.24 K. The susceptibilities both parallel and perpendicular to the Kagomé lattice collapse to almost zero at the lowest temperature, which indicates a nonmagnetic ground state. The temperature dependence suggests that the gap energy of the magnetic state is about 0.25 K.
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Hiroshi Yamamoto, Masayasu Ishikawa
Subject area: Magnetic properties and materials.
1997 Volume 66 Issue 4 Pages
965-966
Published: April 01, 1997
Released on J-STAGE: October 01, 1999
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We report on the magnetic properties of PrFeGe
3, which exhibits no phase transitions from 0.5, K to room temperature. A Curie-Weiss fit of the magnetic susceptibility above 50, K gave a Weiss temperature of -1.6, K and an effective moment of 3.47, μ
B/Pr, which is close to the value of a Pr
3+ free ion. The T-linear term γ of the low-temperature specific heat is 17, mJ/mol, K
2, and the Debye temperature θ
D obtained from the specific heat is 230, K. The magnetic contribution to the specific heat and the electrical resistivity may be explained by a crystalline electric field (CEF) level scheme which extends over hundreds of degrees.
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Kichizo Asai, Osamu Yokokura, Masaru Suzuki, Takashi Naka, Takehiko Ma ...
Subject area: Magnetic properties and materials.
1997 Volume 66 Issue 4 Pages
967-970
Published: April 01, 1997
Released on J-STAGE: October 01, 1999
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The pressure dependence of the 100, K spin-state transition in LaCoO
3 is investigated through magnetization measurement under pressures of up to 18.2, kbar. The energy gap, Δ, between the low-spin ground state and the excited magnetic state (intermediate spin) increases remarkably with increasing pressure. The linear part of the pressure dependence of Δ, which is dominant below 5, kbar, is interpreted consistently by the volume expansion due to the spin-state transition under ambient pressure. In the higher pressure region, a quadratic pressure dependence is dominant, which suggests a very steep volume dependence of the energy of the excited magnetic state under the highly compressed condition.
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Yoshitami Ajiro, Tetsuya Uchikawa, Takayuki Asano, Mamoru Mekata, Naok ...
Subject area: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
1997 Volume 66 Issue 4 Pages
971-974
Published: April 01, 1997
Released on J-STAGE: October 01, 1999
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The unique singlet ground state of an S=1 one-dimensional antiferromagnet is studied using the ESR measurements on NENP, Ni(C
2H
8N
2)
2NO
2(ClO
4). The pure crystal is ESR insentitive in its ground state, reflecting a nonmagnetic nature of the Haldane state. The addition of the nonmagnetic Zn
2+ impurities, however, makes the system ESR sensitive, giving an angle-dependent ESR spectrum. A new interpretation is proposed that the observed signals are due to the S=1/2 broken valence bond which is subjected to the field-induced staggered internal fields originating from the underlying antiferromagnetic polarization.
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Akinori Etoh, Hiroyasu Itoh, Shigeki Mitaku
Subject area: Biophysics.
1997 Volume 66 Issue 4 Pages
975-978
Published: April 01, 1997
Released on J-STAGE: October 01, 1999
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The denaturation kinetics of bacteriorhodopsin induced by light irradiation was measured in the temperature range between 80 and 86°C, which was just above the melting point of the two-dimensional crystal composed of bacteriorhodopsin molecules in the purple membrane. Bacteriorhodopsin was stable in the dark but gradually denatured under the irradiation of visible light longer than 520, nm. Analyzing the time course of the light-induced denaturation phenomenon, the kinetic constant of the denaturation from a photointermediate state was estimated. The temperature dependence of the kinetic constant lead to the effective activation energy of about 41, kcal/mol. The stability of a photointermediate state was discussed on the basis of the light-induced denaturation behavior.
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Heung Geun Oh, Shinsuke Watanabe
Subject area: Mathematical methods in physics.
1997 Volume 66 Issue 4 Pages
979-983
Published: April 01, 1997
Released on J-STAGE: October 01, 1999
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An equilibrium solution is obtained analytically for a nonlinear and dispersive wave with weakly unstable and dissipative conditions. Based on a cnoidal wave solution to the Korteweg-de Vries (K-dV, for short) equation, the second order solution is obtained by taking into account the unstable and dissipative effects. These effects impose some restrictions on the cnoidal wave even when the effects are weak, that is, the relation between the wave-length and amplitude of the cnoidal wave appears which is not the case for the K-dV equation. The explicit second order solution brings about asymmetry in the wave form.
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Shinsuke Watanabe, Shingo Ishiwata, Katsuyuki Kawamura, Heung Geun Oh
Subject area: Mathematical methods in physics.
1997 Volume 66 Issue 4 Pages
984-987
Published: April 01, 1997
Released on J-STAGE: October 01, 1999
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A method of renormalization has been applied to a nonlinear differential equation which describes, in the continuum approximation, a weak shock wave propagating in a dissipative nonlinear LC circuit. In the lowest order of approximation, a well-known Burgers equation is derived. In the next order, a higher order equation which brings about correction to the Burgers equation is obtained. This equation contains secular terms and a term whose particular solution does not satisfy a boundary condition. A method of renormalization is introduced to eliminate such secular terms and an improper particular solution violating a boundary condition. It is shown that the renormalized solution can be described by the Burgers shock wave with the modifications in the width and the velocity.
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Hideyuki Mizuta, Miki Wadati
Subject area: Mathematical methods in physics.
1997 Volume 66 Issue 4 Pages
988-994
Published: April 01, 1997
Released on J-STAGE: October 01, 1999
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Thermodynamic quantities of solvable models such as one--dimensionalHeisenberg model can be obtained through the finite temperature Baxterformula. For the low--temperature expansions, the estimate of the finitesize corrections by use of the Euler--Maclaurin formula is essential.There has been a question on the convergence of such calculations.In this paper, choosing the XX model as a simple example, we showexplicitly that the Euler--Maclaurin formula reproduces the correctlow--temperature expansion of the free energy.
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Eqab M. Rabei
Subject area: Mathematical methods in physics.
1997 Volume 66 Issue 4 Pages
995-997
Published: April 01, 1997
Released on J-STAGE: October 01, 1999
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A singular system with primary constraints of the first kind and a singular system with primary and secondary constraints are investigated.The equations of motion for these systems are written as total differential equations and the set of Hamilton jacobi partial differential equations is obtained. Besides, it is shown that the original action (in configuration space) can be recovered from the Hamiltonian formulation (in phase space) using the inverse of the Legender transformation without introducing the Lagrange multipliers. The equations of motion are integrable iff the total differential of the primary constraints is equal to zero.
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Hiroshi Baba, Atsushi Shinohara, Tadashi Saito, Naruto Takahashi, Akih ...
Subject area: Nuclear decay and radioactivity.
1997 Volume 66 Issue 4 Pages
998-1009
Published: April 01, 1997
Released on J-STAGE: October 01, 1999
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A method to determine a unique J-window in the fission process was devised and the fissioning nuclide associated with thus extracted J-window was identified for each of the heavy-ion reaction systems. Obtained fission barriers at the resulting J-window were compared with the calculated values by the rotating finite range model (RFRM). The deduced barriers for individual nuclides were compared with the RFRM barriers to reproduce more or less the angular momentum dependence the RFRM prediction. The deduced systematic behavior of the fission barrier indicates no even-odd and shell corrections are necessary. The nuclear dissipation effect based on Kramer's model revealed substantial reduction of the statistically deduced barrier heights and brought a fairly large scattering from the RFRM J-dependence. However, introduction of the temperature-dependent friction coefficient (γ = 2 for T ≥q 1.0 MeV and 0.5 for T < 1.0 MeV) was found to bring about satisfactory agreement with both RFRM fission barriers and the pre-fission neutron multiplicity systematics.
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I. Ahmad, M. A. Alvi
Subject area: Nuclear reactions and scattering: general.
1997 Volume 66 Issue 4 Pages
1010-1014
Published: April 01, 1997
Released on J-STAGE: October 01, 1999
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Applying simple considerations we obtain a model for calculating Glauber nucleus-nucleus elastic scattering amplitude in which the two colliding nuclei are treated on the same footing and which has the simplifying features of the rigid projectile model. Taking
4He--
4He elastic scattering as an example we compare the predictions of this and the optical limit and the rigid projectile models with the full Glauber calculation in two approaches. In one the problem is formulated in terms of the intrinsic densities and in the other in terms of the model densities and the associated centre of mass correlation correction factor. It is found that the working of a given model depends much upon the approach adopted for evaluating the amplitude.
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A. S. Chaves, J. F. Sampaio, V. B. Kokshenev, M. C. Nemes
Subject area: Heat flow, thermal and thermodynamic processes.
1997 Volume 66 Issue 4 Pages
1015-1017
Published: April 01, 1997
Released on J-STAGE: October 01, 1999
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A thermal diffusion process is discussed, that should be expected in any system in which the difference in the local susceptibilities χ
T-χ
S is inhomogeneous, where the superscripts indicate isothermal and adiabatic processes. That constitutes an universal secondary response of disordered systems which must be considered in conjunction with the primary “mechanical” response. The response function due to thermal diffusion behaves asymptotically as e^{-(t/τt)^1/2} for short times and as t
-3/2 for long times, but can be interpolated by e
-(t/T)0.60 for a wide range of times around T. The thermal diffusion process can be particularly relevant in the response of magnetic glasses, electric dipole glasses, and in multidomain ferroelectric/ferromagnetic systems with more than two domain orientations.
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Takao Yoshinaga
Subject area: Fluid dynamics.
1997 Volume 66 Issue 4 Pages
1018-1023
Published: April 01, 1997
Released on J-STAGE: October 01, 1999
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Oscillatory solitary waves are analytically examined in a resonant system between long gravity and short capillary waves. Applying the procedure of the normal form analysis to the interaction equation for steady state, weakly nonlinear amplitude equations are derived. Solitary wave solutions of the equations are shown to be in good agreement with numerical results in both long and short wave modes, as far as the wave amplitudes are small. Integrability of the interaction system is briefly discussed in the parameter region where the solutions exist.
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Kazuhiko Omote, Yoshio Waseda
Subject area: Structure of liquids and solids; crystallography.
1997 Volume 66 Issue 4 Pages
1024-1028
Published: April 01, 1997
Released on J-STAGE: October 01, 1999
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A new method has been proposed for estimating the effective pair potentials of a molten salt from the experimental structural data. The basic idea was taken from a “predictor-corrector method” originally proposed by Reatto et al. in 1986 for a single component liquid system. The present method appears to hold promise in reducing difficulty associated with a 1/Q
2 singularity arising from the long-range 1/r behavior of the direct correlation function for a Coulombic interacting liquid. The usefulness of this method was tested by estimating the effective pair potentials of molten NaCl, considering one of the typical ionic liquids, from the experimental structural data reported by Biggin and Enderby in 1982. The resultant potentials are found to improve those of Tosi and Fumi extensively used.
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Satoru Kunii, Jean M. Effantin, Jean Rossat–Mingnod
Subject area: Lattice dynamics and crystal statistics.
1997 Volume 66 Issue 4 Pages
1029-1032
Published: April 01, 1997
Released on J-STAGE: October 01, 1999
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Lattice dynamics of CeB
6 has been studied by an inelastic neutron scattering experiment. The acoustic and optical modes of dispersion curves are measured in the high symmetry directions of the crystal by the triple-axis spectrometers. Flat low-frequency Ce-modes are similar as in LaB
6 but about 1, meV lower in energy than those in LaB
6. Those little differences of the flat modes between CeB
6 and LaB
6 explain the so-called magnetic specific heat anomaly at around 40, K in CeB
6 reported previously.
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Yoshihiro Kuroiwa, Akio Konishi, Takahisa Shobu, Yukio Noda, Kazuhiro ...
Subject area: Lattice dynamics and crystal statistics.
1997 Volume 66 Issue 4 Pages
1033-1043
Published: April 01, 1997
Released on J-STAGE: October 01, 1999
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Neutron scattering studies have been performed to elucidate the martensitic transformation mechanism in a quenched Cu
61Zn
39 alloy. The TA
1[110] phonon branch (e//[1$macr10]) showed slight softening over the entire q-region in the parent phase as the transformation temperature was approached on cooling. No particular dip was observed even just above the transformation temperature, while the intensities of the quasi-elastic diffuse scattering developed near q=1/6[1\bar{1}0] and 1/3[1\bar{1}0] positions in the parent phase. No anomaly was found in several other phonon branches. The structure of the β
1′′ martensite phase was investigated, and a mixed phase of an orthorhombic structure and a monoclinic structure is proposed, which are both different from the previously reported structures. An annealing effect was observed to confirm the role of inclusions in the parent phase.
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Takashi Nikami, Masaharu Tokunaga
Subject area: Equations of state, phase equilibria, and phase transitions.
1997 Volume 66 Issue 4 Pages
1044-1049
Published: April 01, 1997
Released on J-STAGE: October 01, 1999
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A theoretical origin of the anisotropic neutron critical scattering observed in DKDP is studied on the basis of the H
2PO
4 dipole order-disorder model and the ice rule constraint in KDP type ferroelectrics. A radical D
2PO
4 is assumed to take six Slater configurations described by a six states rotator. The diffused scattering intensity is given in terms of neutron scattering structure factors for respective six configurations and correlation functions among six states rotators. The scattering intensity contour in the reciprocal lattice space is numerically computed and shown to be similar to the experimental results even if the rigid ice constraint is released to some extent. Discussions are made on the controversy between the proton tunneling model and the H
2PO
4 dipole order-disorder model from these results.
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Genta Masada, Keisuke Tajima
Subject area: Equations of state, phase equilibria, and phase transitions.
1997 Volume 66 Issue 4 Pages
1050-1053
Published: April 01, 1997
Released on J-STAGE: October 01, 1999
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The time evolution of the first order magnetic phase transition in Er has been studied by X-ray diffraction with the single crystal sample which has a broad mosaic structure. The repetition of the heat cycles across the Curie temperature causes the broad mosaic structure, but this is found to exist only at the surface of the sample. The behavior of the time dependence of the phase transition in a region of broad mosaic structure of the sample differs qualitatively with that of the initial state of the crystal. The coexistence of the two magnetic phases has been observed in a certain narrow temperature range. A model for “pinning” the evolution of the stable phase by crystal defects has been proposed.
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Masahide Sato, Makio Uwaha
Subject area: Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties).
1997 Volume 66 Issue 4 Pages
1054-1062
Published: April 01, 1997
Released on J-STAGE: October 01, 1999
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We study time evolution of parallel straight stepswith repulsive interaction between steps. If step kinetics is asymmetric in the upper and thelower terraces (Schwoebel effect), a vicinal face becomes unstable when undersaturation exceeds a critical value, and an array of large bunches described by the Benney equation appears.In the one-sided model (the extreme limit of the asymmetry)a pairing instability occurs.In this case the instability always ends up with formation of step pairs, and with large undersaturation hierarchical bound states of step pairs are formed.On the contrary many-body bound statesappear in the general asymmetric model.
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Kiyosi Terao, Hideji Yamada
Subject area: Electron states in condensed matter.
1997 Volume 66 Issue 4 Pages
1063-1065
Published: April 01, 1997
Released on J-STAGE: October 01, 1999
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Ab initio band calculations for ScCo
2 with cubic Laves phase structure are carried out as a function of lattice constant, by using the LMTO-ASA method based on the local spin-density-functional formalism. Magnetic energies are also obtained by means of the fixed spin-moment method as a function of total magnetic moment, as well as lattice constant. The critical field of the metamagnetic transition is obtained as 135 T and about 740 T at the observed and theoretical lattice constants.
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Tsuneya Ando
Subject area: Electron states in condensed matter.
1997 Volume 66 Issue 4 Pages
1066-1073
Published: April 01, 1997
Released on J-STAGE: October 01, 1999
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Exciton energy levels and corresponding optical spectra are calculated in carbon nanotubes (CN) in the conventional screened Hartree-Fock approximation within a k·p scheme.The Coulomb interaction gives rise to several exciton bound states as well as the increase of the energy gap.The exciton energy is shifted to higher energy side than the unperturbed band gap because the effect on the band gap is larger.The considerable amount of the optical intensity is transferred to exciton bound states because of the one-dimensional nature of CN's.
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Takashi Ikeda, Hideyuki Kobayashi, Yoshihiro Ohmura, Hirohide Nakamats ...
Subject area: Electron states in condensed matter.
1997 Volume 66 Issue 4 Pages
1074-1078
Published: April 01, 1997
Released on J-STAGE: October 01, 1999
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We present the results of molecular-orbital calculations for alkaline-earth fluorides, i.e., CaF
2, SrF
2 and BaF
2.The discrete variational (DV) Xα method is applied to two types of model clusters, i.e., one centered at the cation site and the other at the anion site. Electrostatic potential due to the ions outside the cluster has been calculated with direct summation of the Coulomb potential of point charges by the Coker's method.The electronic structures obtained by the present models agree well with those obtained by photoelectron spectroscopy.The outer-most Ba
2+ 5p core band is found to have a width of less than 2 eV which is much smaller than the proposed value in interpreting the excitation spectrum of Auger free luminescence and the total photoelectric yield spectrum.The ionic radii of alkaline-earth and fluorine ions in CaF
2, SrF
2 and BaF
2 are determined by investigating the charge distribution. The ionic radii thus obtained are in good agreement with the crystal values of Shannon and Prewitt.
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Takashi Ikeda, Hideyuki Kobayashi, Yoshihiro Ohmura, Hirohide Nakamats ...
Subject area: Electron states in condensed matter.
1997 Volume 66 Issue 4 Pages
1079-1087
Published: April 01, 1997
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We present the results of molecular-orbital calculations for BaF
2. The discrete variational (DV) Xα cluster method is applied to calculations of Auger-free luminescence (AFL) spectrum and X-ray absorption near edge structure (XANES). The AFL spectrum is analyzed by making use of level structures of the model cluster. The theoretical spectrum reproduces well the characteristics of the experimental one. Only the physical process corresponding to the 5.6 eV emission in AFL is found to be localized. The X-ray absorption spectrum for Ba O
2, 3 edge in BaF
2 is calculated and compared with the excitation spectrum of AFL at 5.6 eV in BaF
2. The theoretical absorption spectrum reproduces well the characteristics of the experimental excitation spectrum of AFL in the energy range less than 10 eV from the edge.
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Kaoru Iwano
Subject area: Electron states in condensed matter.
1997 Volume 66 Issue 4 Pages
1088-1096
Published: April 01, 1997
Released on J-STAGE: October 01, 1999
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The relaxations occurring after photoexcitation in the MX chains are investigated, using a one-dimensional extended Peierls-Hubbard model.The special emphasis is placed on the processes in which the nonlinear excitations such as solitons and polarons are created in the background of the charge-density wave (CDW).The way of relaxations changes its nature, depending mainly on the relative strengthsof the on-site and nearest-neighbor Coulombic repulsions U and V, respectively, to the on-site electron-lattice interaction S. When U or both U and V dominate over S, soliton-pair states are unstable compared with the self-trappedexciton (STE) in the localized limit of the model.However, the neutral-soliton pair can be the lowest structural excitation inintermediate-transfer cases, stabilized by the effect of itineracy. As for the adiabatic potential surfaces, the uniform CDW is connected to the neutral-soliton pair, while the STE to the charged-soliton pair. It is expected that the STE will make atransition to the neutral-soliton pair nonadiabatically.When S dominates over U and V, on the other hand, the charged-soliton pair is the lowest structural excitation even in the localized limit. In those cases, the uniform CDW is connected to the charged-soliton pair, while the STE to theneutral-soliton pair on the same potential surfaces.Following these considerations, the calculation of the photoinduced absorption is also performed assuming that the former case is realistic. The obtained spectrum in the presence of a neutral soliton is compared with the experimental result.
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Ryusuke Kondo, Tatsuo Hashimoto, Keiichi Edagawa, Shin Takeuchi, Tsune ...
Subject area: Electronic transport in condensed matter.
1997 Volume 66 Issue 4 Pages
1097-1102
Published: April 01, 1997
Released on J-STAGE: October 01, 1999
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The electrical resistivity and the magnetoresistance have been measured for icosahedral phases of Zn--Mg--RE (RE=Y, , Gd). Electrical resistivities of bulk samples of Zn
56Mg
36Y
8, annealed ribbon samples of Zn
62Mg
30Y
8 and annealed ribbon samples of Zn
55Mg
35.5Gd
9.5 are 1, mΩ cm, 0.3, mΩ cm and 0.3, mΩ cm, respectively. The resistivities of all the samples decrease by 5-- 7$T
1/2 dependence, while the resistivity of Zn--Mg--Gd obeys ln T dependence, where Gd atoms bear magnetic moments. In Zn--Mg--Y, the magnetoresistance is negative and insensitive to temperature, while in Zn--Mg--Gd it is positive in a low field range and becomes negative at high field with its magnitude larger at lower temperature. These results are interpreted by the theories of electron-electron interaction, weak localization and s-d exchange interaction.
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Kazuki Kanki, Kosaku Yamada
Subject area: Electronic transport in condensed matter.
1997 Volume 66 Issue 4 Pages
1103-1108
Published: April 01, 1997
Released on J-STAGE: October 01, 1999
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The effects of electron-electron interactions on cyclotron resonance frequency are analyzed on the basis of the Fermi liquid theory. In Galilean invariant systems the cyclotron resonance frequency is independent of electron-electron interactions (Kohn's theorem). This theorem is due to the backflow effect by which the momentum conservation law is recovered. Umklapp processes tend to reduce the resonance frequency from the cyclotron frequency of non-interacting electrons.
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M. C. Refolio, J. M. López Sancho, J. Rubio, M. P. López ...
Subject area: Electronic structure and electrical properties of surfaces, interfaces and thin films.
1997 Volume 66 Issue 4 Pages
1109-1114
Published: April 01, 1997
Released on J-STAGE: October 01, 1999
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In order to account for strong correlation effects, we have carried out a many body calculation of the electronic structure of the Cl/Si(100)-(2× 1) system. The one-electron Green function is found directly from its Lehmann representation in terms of N-1 and N+1 electron states. These are obtained approximately by means of an iteration scheme (the lattice-configuration approach) whereby states with an increasing number of electron-hole pairs are successively included. This approach gives in a natural way the configurational composition of all the spectral features, which allows following in detail the character of possible relaxation processes. The resulting density of states is in quantitative agreement with the photoemission spectrum and describes qualitatively the desorption data of positive and negative Cl ions. It is found that most of the above spectral features are dominated by a strong shake-up of electron-hole pairs which largely invalidates a one-electron picture. This is ultimately traced to the (probably nonlinear) substrate response to the strong disruption produced by the Cl atoms (of large electronegativity).
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Yoshinori Yamamoto, Hitoshi Ohta, Mitsuhiro Motokawa, Osamu Fujita, Ju ...
Subject area: Magnetic properties and materials.
1997 Volume 66 Issue 4 Pages
1115-1123
Published: April 01, 1997
Released on J-STAGE: October 01, 1999
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The g-shifts in spin-Peierls (SP) and magnetic (M) phases of the inorganic spin-Peierls material CuGeO
3 have been observed by submillimeter wave ESR. The temperature dependence of the g-shifts from U phase to SP or M phase showed a continuous change. Since such g-shifts were also observed in the organic spin-Peierls material, for example TTF-AuBDT, such g-shifts can be considered the universal phenomena due to the lattice distortion in the spin-Peierls materials. But, in the case of CuGeO
3, the g-shifts are so large that we cannot explain them in the framework of the point charge model with considering the continuous lattice distortion.
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Kiyoichiro Motoya, Keisuke Nakaguchi, Noriaki Kayama, Kazunori Inari, ...
Subject area: Magnetic properties and materials.
1997 Volume 66 Issue 4 Pages
1124-1129
Published: April 01, 1997
Released on J-STAGE: October 01, 1999
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Magnetic susceptibility, specific heat, nuclear magnetic resonance and neutron diffraction measurements have been made to investigate the magnetic property of a ternary compound CeNiC
2. Temperature variations of magnetic susceptibility and specific heat suggest that magnetic transitions take place at T=20, K, 10, K and at 2.2, K. NMR line width of
13C nuclei increases remarkably below T=20, K indicating the increase of transferred hyperfine field due to magnetic order. In the neutron diffraction pattern below T=20, K, additional peaks appear which indicate the presence of long-range magnetic order. Based on these measurements, a magnetic structure model of CeNiC
2 which involves a transition from an incommensurate to a commensurate antiferromagnetic order is presented.
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Kenji Ikushima, Hiroshi Yasuoka, Akira Ohno, Hidenori Takagi, R. J. Ca ...
Subject area: Magnetic properties and materials.
1997 Volume 66 Issue 4 Pages
1130-1137
Published: April 01, 1997
Released on J-STAGE: October 01, 1999
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The
61Ni spin-lattice relaxation rate,
61T
1-1, and the Knight shift of a 91\sample of LuNi
2B
2C have been measured in the normal state.It was found that
61(T
1T)
-1 shows a Curie-Weiss like behavior, while the Knight shift has a slight temperature dependence.The hyperfine coupling constant is estimated to be
61A=-16 kOe/μ
B, which is an order of magnitude smaller than thatdue to the 3d-core-polarization mechanism.When the orbital term of the relaxation rate is given by theformula calculated for the tetragonal (D
2d) symmetry at the
61Ni sites, much larger d-spin term than that expected from the Knight shift is obtained. The Korringa relation is also discussed on the assumption that the hyperfine coupling constantis reduced by a strong s-d admixture, and thenthe deviation from the Korringa relation for free electrons, K(α), is more than one. This result suggests the significance of the generalizedsusceptibility, χ(q), at finite wave vectors.
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Shin–ichi Shamoto, Katsuaki Kodama, Hiroshi Harashina, Masatoshi ...
Subject area: Magnetic properties and materials.
1997 Volume 66 Issue 4 Pages
1138-1144
Published: April 01, 1997
Released on J-STAGE: October 01, 1999
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Neutron diffraction and inelastic scattering studies have been carried out on a single crystal of BaCo
0.82Ni
0.18S
2. Analyses of the form factor show that the system is in the high spin state. Two-dimensional nature of the magnetic system has clearly been shown from the q-dependence of the magnetic excitations both above and below T
N. It is shown that a random phase treatment can roughly describe characteristics of the magnetic excitations above T
N.
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Noriko Tanemura, Yoshikazu Suzumura
Subject area: Magnetic properties and materials.
1997 Volume 66 Issue 4 Pages
1145-1152
Published: April 01, 1997
Released on J-STAGE: October 01, 1999
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Fluctuations and thermodynamic quantities of spin density wave (SDW) states with a quarter-filled band have been examined in the presence of the anion potential in organic conductors. The competition between the commensurability energy and the anion potential in the SDW state is demonstrated explicitly by calculating phase diagram, collective modes, spectral weights and susceptibilities.
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Masayoshi Tsukano, Minoru Takahashi
Subject area: Magnetic properties and materials.
1997 Volume 66 Issue 4 Pages
1153-1156
Published: April 01, 1997
Released on J-STAGE: October 01, 1999
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A spin-1/2 Heisenberg model on a ladder, which consists of one ferromagnetic leg and one antiferromagnetic legconnected by antiferromagnetic rungs, is discussed.The phase transition in the groundstate is investigated in such a system.It is shown that the spontaneous magnetization, m, becomes zeroif the interchain coupling R is larger than a critical value R
c.It is found that R
c=1.134461 ± 0.000001 by the exact diagonalization.In the region R
c, we also find that the spontaneous magnetization isproportional to √Rc-R near the critical point Rc.Moreover an exact eigenstate with the total spin S=0 is obtained.
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Kazuaki Murayama, Jun–ichi Igarashi
Subject area: Magnetic properties and materials.
1997 Volume 66 Issue 4 Pages
1157-1164
Published: April 01, 1997
Released on J-STAGE: October 01, 1999
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We study a magnetic impurity coupled to quantum antiferromagnetsin quasi-two dimensions on the basis of the pseudofermion representationfor the impurity spin. The dynamical impurity spin-correlation function andthe impurity susceptibility are calculated. In the Néel phase, we use the self-consistent Born approximation in addition to the spin-wave expansion for the spins in the plane.In the paramagnetic phase, we consider the leading order in the 1/N expansion(the self-consistent ladder approximation) in addition tothe Schwinger-boson-mean-field theory for the spins in the plane.It is shown that the impurity susceptibility obeys the Curie lawat high temperatures and converges to a finite value as T → 0.Relations to the experiments on Nd
2-xCe
xCuO
4 are discussed.
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Yukiyasu Ozeki, Yoshihiko Nonomura, Koji Hukushima
Subject area: Magnetic properties and materials.
1997 Volume 66 Issue 4 Pages
1165-1174
Published: April 01, 1997
Released on J-STAGE: October 01, 1999
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The site-random Ising spin glass model in two dimensions is investigated .The phase diagram is determined in the concentration-temperature planeby the numerical transfer-matrix method.Using the rigorous symmetry found previously, we obtain several exact relations for the order parameters, which provide an insight to the symmetry in the phase diagram.
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Tetsuro Saso
Subject area: Magnetic properties and materials.
1997 Volume 66 Issue 4 Pages
1175-1179
Published: April 01, 1997
Released on J-STAGE: October 01, 1999
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In order to study the effects of strong magnetic field on Kondoinsulators, we calculate magnetization curves and single-particleexcitation spectra of the periodic Anderson model at half-fillingunder finite magnetic field by using the self-consistent second-orderperturbation theory combined with the local approximation which becomes exact in the limit of infinite spatial dimensions. Withoutmagnetic field, the system behaves as an insulator with an energy gap, describing the Kondo insulators. By applying magnetic field tof-electrons, we found that the energy gap closes and the first order transition from insulator tometal takes place at a critical field H
c. The magnetization curve shows a jump at H
c. These are consistent with our previous study in terms of the exact diagonalization.Relationship to the experiments on YbB
12 and some other Kondo insulators isdiscussed.
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Hiroaki Kusunose, Kazumasa Miyake
Subject area: Magnetic properties and materials.
1997 Volume 66 Issue 4 Pages
1180-1186
Published: April 01, 1997
Released on J-STAGE: October 01, 1999
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We investigate a problem about the competition between the hybridization andthe Hund-rule coupling by applying the Wilson numerical renormalization-groupmethod to the extended Kondo model where the impurity spin interactsvia the Hund-rule coupling, with an extra spin which is isolated from theconduction electrons.It is shown that the Hund-rule coupling is an irrelevant perturbation against the strong coupling fixed point.However, the Hund-rule coupling decreases the characteristic energy T
Kdrastically to the lower side and the irrelevant operator, which describes the low energyphysics, takes a form of ferromagnetic exchange interaction between theextra spin and the Kondo resonance states because of the existence ofthe Hund-rule coupling.
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Jun Sugiyama, Tatsumi Hioki, Shoji Noda, Masaaki Kontani
Subject area: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
1997 Volume 66 Issue 4 Pages
1187-1194
Published: April 01, 1997
Released on J-STAGE: October 01, 1999
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Magnetic properties of a polycrystalline sample of LiMn
2O
4 were investigated using a
7Li nuclear magnetic resonance (
7Li-NMR) technique in the temperature range between 4.2 and 300, K. It was found that both the shift (K) and the full width at half maximum (FWHM) of the
7Li-NMR line increased monotonically with lowering temperature from 300 to 40, K, then, increased abruptly at around 40, K and looked to level off to constant values with further lowering temperature. The values of K and FWHM at 4.2, K were estimated to be about 0.7\at 4.2, K seemed to be independent of an external magnetic field. Furthermore, the temperature dependence of a spin-lattice relaxation rate (T
1-1) exhibited a sharp maximum at around 40, K. These results indicated that the moments of Mn ions ordered antiferromagnetically below the Néel temperature T
N=40, K.
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