63 巻, 3 号
選択された号の論文の56件中1～50を表示しています
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Yoshimasa Nakamura
専門分野: Mathematical methods in physics.
1994 年 63 巻 3 号 p.
827-829
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
Stochastic Lax representations of stochastic differential equations associated with random collision models are found.
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Takashi Nagatani
専門分野: Statistical physics and thermodynamics.
1994 年 63 巻 3 号 p.
830-833
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
A simple aggregation model with creation is presented to study the scaling behavior. The model is an extended version of the coalescing random walker model to take into account creation and the mass-dependent transition probability. The mass s of a particle is created at the rate s
μ (μ <1), moves ahead one step with transition probability T=a+bs
-α (α >0, a, , b>0 and a+b≤ 1), and is stopped with probability 1-T. The aggregation shows an interesting scaling behavior in competition with creation. It is shown that the mean mass ‹ s› of particle scales as ‹ s› ≈ t
β where t is time. The scaling relation β =max, [1/(1+α ), , 1/(1-μ )] is found for a=0.0. For a>0, the scaling relation β =max, [1/2, , 1/(1+α ), , 1/(1-μ )] is satisfied. The scaling relation is consistent with that derived from a simple scaling argument.
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Koichi Ogura, Takemasa Shibata
専門分野: Experimentally derived information on atoms and molecules: instrumentation and techniques.
1994 年 63 巻 3 号 p.
834-838
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
Population of metastable levels in a gadolinium atomic beam produced by electron beam heating were measured using the resonance photoionization technique. The population followed the Boltzmann distribution and the atomic excitation temperature was determined. The atomic excitation temperature is far lower than the temperature of the evaporation surface and nearly equal to the temperature which characterizes the distribution in the velocity component parallel to the gadolinium atomic beam axis. This suggests that the atomic excitation energy and the translational energy exchange each other at high reaction rate in the atomic vapor expanding from the evaporation surface into vacuum.
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Toshiharu Mitsui, Ken–ichi Machida, Tetsuya Kato, Katsunori Iio
専門分野: Equations of state, phase equilibria, and phase transitions.
1994 年 63 巻 3 号 p.
839-842
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
A hexagonal antiferromagnet RbFeBr
3 was found to undergo successive structural phase transitions at T
I (=109.0, K) and T
c (=34.4, K) and to be ferroelectric along the hexagonal c-axis below T
c. RbFeBr
3 is a new type of ferroelectric crystal, the crystal structure of which is characterized by linear chains of face-sharing octahedra (FeBr
6)
4- along the c-axis (h-h-h packing). The ferroelectricity in RbFeBr
3 is attributed to possible shifts of two-thirds of the chains antiparallel to the remaining one-third along the c-axis, which are possible due to the crystal symmetry of P6
3cm below T
c.
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Tadao Kasuya
専門分野: Electron states in condensed matter.
1994 年 63 巻 3 号 p.
843-846
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
The magnetic polaron model developed recently in the study of Ce monopnictides was applied to Yb monopnictides. Anomalous properties seen in the studies of neutron scattering, specific heat, magnetic measurement, etc., were explained consistently. In YbSb, a novel singlet ground state with large ferromagnetic fluctuation is expected to be formed.
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Yasuaki Oohara, Setsuo Mitsuda, Hideki Yoshizawa, Nariyasu Yaguchi, Hi ...
専門分野: Magnetic properties and materials.
1994 年 63 巻 3 号 p.
847-850
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
The magnetic ordering of AgCrO
2, a rhombohedrally stacked triangular-lattice antiferromagnet with Heisenberg spin S=3/2, has been studied by magnetic susceptibility measurement and neutron diffraction on a powder sample. The magnetic phase transition temperature was determined to be 24, K. The magnetic peaks appear at (0.327 {1em}0.327 {1em}0) in hexagonal units, which shows that the magnetic structure is a modulated 120° structure. The modulation is due to the competition between the intraplane and interplane interactions. The magnetic peaks are broad, indicating that this strong competition suppresses the development of the true long-range order in AgCrO
2 below 24, K.
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Masatoshi Imada
専門分野: Magnetic properties and materials.
1994 年 63 巻 3 号 p.
851-854
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
A phenomenological theory of the antiferromagnetic correlations in cuprates is constructed from analyses of recent numerical results of the Hubbard model. Two crossover temperatures are predicted to exist. In three regions divided by the two crossover temperatures, we present a qualitative but explicit form of doping and temperature dependences of the dynamical susceptibility χ (q, , ω ), which agrees with NMR and neutron scattering data of cuprates. It solves recent controversy between these two experimental results and provides us with a unified picture of antiferromagnetic correlation in cuprates.
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Shinji Yuasa, Hideki Miyajima, Yoshichika Otani, Kazuhiko Tsuji, Yoshi ...
専門分野: Magnetic properties and materials.
1994 年 63 巻 3 号 p.
855-858
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
Magnetic phase transitions in bcc FeRh
0.95Ir
0.05 alloy were investigated under high pressures up to 6.2, GPa by means of X-ray diffractometry using synchrotron radiation. The phase transition from antiferromagnetic to paramagnetic at high pressures with increasing temperature was confirmed to be a first-order phase transition accompanied by a volume expansion of about 0.3
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Yoshitami Ajiro, Takayuki Asano, Toshiya Inami, Hiroko Aruga–Kat ...
専門分野: Magnetic properties and materials.
1994 年 63 巻 3 号 p.
859-862
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
The high-field magnetization process of a one-dimensional S=1/2 trimer system, 3CuCl
2· 2dioxane, is studied on powder samples using a pulse magnet up to 30, T between 1.5, K and 9, K. The magnetization increases nonlinearly and saturates around 15, T, characteristic of low-dimensional Heisenberg antiferromagnets. The magnetization data are consistent with a previously proposed model in which ferromagnetic trimers composed of three S=1/2 spins are weakly coupled antiferromagnetically to form a S=3/2 antiferromagnetic chain. Based on this model, the antiferromagnetic intertrimer interaction is directly derived as J
AF=-16.2, K. However, the observed magnetization curve suggests that a composite spin system consisting of three S=1/2 spins has more of a quantum nature than does a genuine S=3/2 system, because the ferromagnetic intratrimer interaction is not sufficiently strong.
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Masaaki Kontani, Hiroshi Ido, Takashi Nishioka, Hideko Ando, Yoshitaka ...
専門分野: Magnetic properties and materials.
1994 年 63 巻 3 号 p.
863-866
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
We report magnetic susceptibility, electrical resistivity and specific heat measurements on single-crystal specimens of Ce
2Cu
8Al
9 with the rhombohedral Th
2Zn
17-type crystal structure. The low-temperature specific heat has revealed heavy-fermion behavior, i.e., C/T attaining an extremely large value of about 2.7, J/K
2, mol-Ce around 0.7, K, which is greatly reduced by an applied magnetic field, namely, down to less than half of the zero-field value for H=5.2, T. It is indicated from the present experiments that Ce
2Cu
8Al
9 is a new heavy-fermion material of T
K-- 3, K.
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Tôru Sakai, Hiroyuki Shiba
専門分野: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
1994 年 63 巻 3 号 p.
867-871
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
In order to explain some mysteries in ESR experiments on NENP, we study the S=1 antiferromagnetic chain with a transverse staggered magnetic field. The staggered field is caused by the crystal structure of NENP and makes the ESR absorption possible from the ground state to the lowest excited state with k=π . In addition it removes the phase transition, which was predicted for the Heisenberg model without the staggered field. Numerical diagonalization study on this model qualitatively agrees with the NMR, ESR and heat capacity measurements. In particular, it explains well the field dependence of the energy gap, the intensity of ESR and the staggered moment. It is also found that the standard theory of ESR is valid above the “critical field” corresponding to a minimum of the energy gap, if the sublattice moments are suitably reinterpreted.
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Jun Kikuchi, Hiroshi Yasuoka, Masashi Hase, Yoshitaka Sasago, Kunimits ...
専門分野: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
1994 年 63 巻 3 号 p.
872-875
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
We have observed the nuclear quadrupole resonance (NQR) of Cu in the spin-Peierls system CuGeO
3. The NQR signals have been observed at 34.23± 0.02, MHz for
63Cu and 31.66± 0.02, MHz for
65Cu at 4.2, K under zero external field. These signals persist down to 1.3, K with neither line splitting nor broadening due to the internal magnetic field. This fact indicates there is no long-range order of Cu spins. The
63Cu nuclear spin-lattice relaxation rate
63(1/T
1) rapidly drops below 15, K which clearly demonstrates an opening of the energy gap in the excitation spectrum. However, no anomaly was detected in the Cu NQR frequency at the transition temperature. It was also found that
63(1/T
1) above 15, K smoothly extrapolates to a finite value at 0, K. This may suggest the spin dynamics in the paramagnetic state is described in terms of the one-dimensional antiferromagnetic Heisenberg model with S=1/2.
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Takashi Umeki, Kenichiro Yagi, Hikaru Terauchi
専門分野: Dielectric properties and materials.
1994 年 63 巻 3 号 p.
876-878
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
X-ray diffraction study on K
1-x(NH
4)
xI mixed crystal with x=0.5 has been carried out to determine the order parameter in the glassy phase. Deviation of the lattice parameter from the Debye approximation was seen in the glassy phase where the diffuse scattering was observed at the (500) reciprocal lattice point. Both the deviation of lattice parameter and the intensity of diffuse scattering increased with decreasing temperature. The results indicate that there is a local distortion which breaks the fcc symmetry in the glassy phase.
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Kiyoshi Sogo
専門分野: Mathematical methods in physics.
1994 年 63 巻 3 号 p.
879-884
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
Complete set of solutions for the Calogero-Sutherland-Moser model is obtained exactly. The eigenfunctions are given by the homogeneous Laurent polynomials.
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Saburo Kakei, Junkichi Satsuma
専門分野: Mathematical methods in physics.
1994 年 63 巻 3 号 p.
885-894
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
Multi-soliton solutions of a coupled system of the nonlinear Schrödinger equation and the Maxwell-Bloch equations are given. Solutions of the system are explicitly constructed as a quotient of Casorati-type determinants. By using explicit form of the soliton solutions, the influence of the MB-term on the speed of soliton is evaluated.
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Hiroki Kokubo, Masaki Sano, Beatrice Janiaud, Yasuji Sawada
専門分野: Statistical physics and thermodynamics.
1994 年 63 巻 3 号 p.
895-903
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
A localized target pattern is observed in the grid pattern of the electro-hydrodynamic convection of a nematic liquid crystal. The target pattern is created by a phase instability through the coupling between the oscillation of an underlying grid and the deformation of the grid. By determining the coefficients of phase equations derived from coupled complex Ginzburg-Landau equations, we confirm that the equations describe the instability in the system. Moreover we found that the critical voltage for Hopf bifurcation depends on the grid wavenumber. This effect explains the localization of target.
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Yoshiki Nakajima, Shigeo Naya
専門分野: Statistical physics and thermodynamics.
1994 年 63 巻 3 号 p.
904-914
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
A microscopic theory is presented to study the two-directional orientational phase transition of the interacting dipolar system and its dynamic susceptibility in the paraelectric phase. On the basis of a classical mechanical model that the librational and the rotational motion for a dipole in the hindered-rotation potential can be treated exactly, the statistical mechanical calculations are carried out in the framework of the molecular field approximation and the linear response theory. In this approximation, several characteristic quantities such as Curie temperature, specific heat, static and dynamic susceptibilities, etc. are all obtained rigorously. The present model recovers the dynamics proper to the dipolar motion in the studies of the orientational phase transition and its dynamic susceptibility, so that it offers an approach different from the conventional pseudo-Ising spin model.
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Takao Yamamoto, Yasuhiro Akutsu, Noriko Akutsu
専門分野: Statistical physics and thermodynamics.
1994 年 63 巻 3 号 p.
915-925
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
Mean-square fluctuation width of a single step on the vicinal surface, denoted by Δ
2(y) (y: distance along the step), is calculated based on the terrace-step-kink picture. For systems with only short-range step-step interactions, both the free-fermion approach and the capillary-wave approach are taken to derive the universal asymptotic behavior Δ
2(y)-- A, log, y with A=(π ρ )
-2, where ρ is the step density. We present a general relation between Δ
2(y) and the surface height-height correlation function, which connects the universal behavior to the universal Gaussian curvature jump at the facet edge. For the case with long-range (inverse-square) step-step interactions, we combine the exact solution of the Sutherland model with the capillary-wave theory. We successfully derive the non-universal amplitude A=A(ρ, , g) as a function of the coupling constant g.
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Hiroki Nakano, Minoru Takahashi
専門分野: Statistical physics and thermodynamics.
1994 年 63 巻 3 号 p.
926-933
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
A modified spin-wave theory is applied to the one-dimensional quantum Heisenberg model with long-range ferromagnetic interactions. ( H=-J∑
ij(r
ij)
-pS
i· S
j). Low-temperature properties of this model are investigated. The susceptibility and the specific heat are calculated; the relation between their behaviors and strength of the long-range interactions is obtained. This model includes both the Haldane-Shastry model and the nearest-neighbor Heisenberg model; the corresponding results in this paper are in agreement with the solutions of both the models. It is shown that there exists an ordering transition at a finite temperature for 1
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Wu Youhong, Mitsukazu Onomichi, Shigeo Sasaki, Hiroyasu Shimizu
専門分野: Molecular spectra and interactions of molecules with photons.
1994 年 63 巻 3 号 p.
934-940
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
High-pressure Raman spectra of liquid and crystalline CH
2F
2 were measured up to 29, GPa at 300, K in a gasketed diamond-anvil cell. Four solid phases have been found; the transition pressures of liquid-solid phase I, phase I-phase II, phase II-phase III and phase III-phase IV were determined to be 2.63, 3.82, 5.9 and 8.2, GPa, respectively. Among these, the solid phase I is an orientationally disordered (plastic) phase. The CH asymmetric stretching ν
6 vibration (B
1) splits into the longitudinal optical (LO) mode and the transverse optical (TO) mode in the liquid and four solid phases. The wavenumbers of LO and TO modes and their wavenumber difference remarkably depend on the pressure, and drastically change at each phase transition point. The wavenumber of the CH stretching ν
1 vibration (A
1) also shows a strong pressure dependence, and this behavior is compared with those of CHF
2Cl and CHF
3.
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Yoh Itoh
専門分野: Molecular spectra and interactions of molecules with photons.
1994 年 63 巻 3 号 p.
941-947
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
The angular distribution of Ar
+ ions produced by one-electron capture process was measured from 0° to 20° with a newly constructed crossed-beam apparatus. Two components were observed in the angular distribution of Ar
+, one component is a sharp peak around 0° and the other is a hump around the reduced scattering angle E
lab· θ
lab=290± 20, eV· deg. Only the following process is considered in the analysis of the experimental results: Ar
2+(
3P)+Ne(
1S
0)→ Ar
+(
2P)+Ne
+(
2P)+6.1, eV. The experimental results were compared with those obtained by pure classical trajectory calculations taking into account simple interaction potentials. The observed Ar
+ ions in the forward peak were considered to be produced in a charge transfer process which occurs in the incoming channel of the trajectory, and the ions in the hump change charge in the outgoing channel.
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Toshio Kawai, Ikushi Yoshida, Isao Imai
専門分野: Heat flow, thermal and thermodynamic processes.
1994 年 63 巻 3 号 p.
948-953
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
Joule's heat generated in a homogeneous body of arbitrary shape flows out just equally through each of two electrodes, when the body is isolated from the environment both electrically and thermally except at the electrodes, which are attached onto the surface of the body. This ``Theorem of equi-partition of Joule's heat'' holds even when both electrical and thermal conductivity of the material vary with temperature in an arbitrary way.
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Kohji Yamamoto, Nobuaki Ikuta
専門分野: Kinetic and transport theory of fluids; physical properties of gases.
1994 年 63 巻 3 号 p.
954-966
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
Adopting the model differential cross sections used by Reid (1979) and by Haddad et al. (1981), an investigation to asses the discrepancies observed in the transverse diffusion coefficients D
T and other transport properties are performed by the Monte-Carlo simulation. The results show that the values of ND
T drastically vary with the change of anisotropy in the scattering property against the common sense that ND
T is determined solely by the reduced field E/N under a given momentum transfer cross section. Cross sections so far derived from the D
T/μ data may be necessary to be reassesed if anisotropy in the scattering properties is considered.
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Kazuaki Hanada
専門分野: The physics of plasmas and electric discharges.
1994 年 63 巻 3 号 p.
967-978
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
Heat flow during sawtooth collapse was studied on the WT-3 tokamak by using temporal evolution of soft X-ray intensity profile in the poloidal cross section in a lower hybrid current driven plasma as well as an electron cyclotron heated plasma. Two phases in sawtooth collapses were observed. In the first phase, the hottest spot that is the peak of the soft X-ray distribution approaches the inversion surface and heat flows out through a narrow gate on the inversion surface. In the second phase, the hottest spot stays on the inversion surface, and heat flows out through the whole inversion surface. This suggests that magnetic reconnection as predicted by Kadomtsev's model occurs in the first phase, but in the second phase, a different mechanism dominates heat flow.
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Kenichi Nanbu
専門分野: The physics of plasmas and electric discharges.
1994 年 63 巻 3 号 p.
979-983
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
Relaxation of ions in a uniform electric field is analyzed by using the theory of stochastic process. Ion-neutral interaction is assumed to be Maxwellian. The drift velocity, the mean energy, and the longitudinal and transverse diffusion coefficients thus obtained agree with the exact solution of the moment equations of the Boltzmann equation.
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Tomonori Koda, Hatsuo Kimura
専門分野: Structure of liquids and solids; crystallography.
1994 年 63 巻 3 号 p.
984-994
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
We study the nematic-smetic A phase transition of binary mixture of parallel hard cylinders of different lengths. We use the Helmholtz free energy truncated at the second virial term. Changing values of q (length of a longer cylinder), x (composition) and η (packing fraction) of the cylinders, we obtained the transition points at which the nematic phase becomes unstable for a sinusoidal density perturbation. Phase diagrams on η vs x plane are drawn for various q's. Depending on q and x, the stable region of the smetic A is suppressed or enlarged, and two types of structures of the smetic A appear. In one type of the structure, each layer of the smetic A contains longer particles and shorter particles uniformly. In the other type of the structure, layer of shorter particles and layer of longer particles stack alternatively.
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Akira Nagasawa, Rie Yamauchi, Kazue Kita, Tomoko Makita, Yukio Morii
専門分野: Lattice dynamics and crystal statistics.
1994 年 63 巻 3 号 p.
995-1000
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
The present study on the [110]TA
1 phonon dispersion relation in a AuCuZn
2 alloy reveals that the lattice instability towards the 18R martensite is characteristic of only the Heusler phase existing stably below about 670, K, which is the disordering temperature to the B2-phase. Anomalous peak appearing near ζ =2/3[110] in the Heusler-phase is also examined by neutron elastic scattering experiments in a wide range of temperature. It is evident that such a peak has no relation to the 2/3-dip on the [110]TA
1 phonon branch observed in the Heusler-phase but it is originated from vacancies existing inherently and regularly in the B2-lattice.
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Susumu Ikeda, Yukio Noda, Hidehiko Sugimoto, Yasusada Yamada
専門分野: Lattice dynamics and crystal statistics.
1994 年 63 巻 3 号 p.
1001-1008
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
Neutron incoherent scattering experiments covering wide energy-momentum space were carried out by utilizing both pulsed neutron source and steady neutron source, in order to elucidate the dynamical properties of the protons in KDP (KH
2PO
4). In the paraelectric phase, no inelastic peaks corresponding to the excitation of the proton tunneling mode was observed within the limit of the instrumental resolution. Instead, strong quasi-elastic scattering was observed extending in a wide energy-momentum space. The experimental results are analyzed consistently based on the `order-disorder' model throughout T
c. However, in order to get reasonable fit for the energy spectra in the paraelectric phase, we have to assume an extraordinary value for the relaxation time of the proton hopping motion as 3× 10
-13, sec, which is of the order of the inverse of the averaged phonon frequency.
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Masaru Komukae, Ken Sakata, Toshio Osaka, Yasuharu Makita
専門分野: Equations of state, phase equilibria, and phase transitions.
1994 年 63 巻 3 号 p.
1009-1017
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
Optical observation of domain structures and X-ray examinations of Cs
3H(SeO
4)
2 were carried out above room temperature. The effect of an external force on the rearrangements of the constituent ions accompanied by the movement of domain boundary was studied at room temperature. The interrelations between unit cells in each phase were obtained above room temperature. When the crystal is warmed up through the phase transition at T
II, all the hydrogen bonds are instantaneously broken, and then the hydrogen atoms are so rearranged as to form new hydrogen bonds between two diffrent adjacent SeO
4-2 tetrahedra. When the domain boundary is moved, the SeO
4-2 tetrahedra are tilted and displaced to new positions, and simultaneously hydrogen bonds are broken, and then new hydrogen bonds are reconstructed.
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Kêichiro Aizu
専門分野: Equations of state, phase equilibria, and phase transitions.
1994 年 63 巻 3 号 p.
1018-1024
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
In this paper, unlike in previous ones, it is assumed that prototypic phases are not homogeneous but artificially incommensurately undulated. Transitions from such prototypic phases to ferroic phases are investigated. As is well known, free energy functions are composed of order parameters, spatial differentiations and coefficients. Unlike previously, not only order parameters are undulated. By prototype undulation, even coefficients are undulated. Those gradient-linear terms which would be extinguished by spatial averaging if prototypic phases were homogeneous, can play important roles. Three cases are studied, one of which is the simplest case conceivable, and in the other two the free energy function contains ∂
z(Q
2α -Q
2β ) and ∂
z(Q
α Q
β ) respectively. An expression of a rise of the transition temperature is obtained. In the latter two cases, expressions of nonzero and non-π phase differences are obtained.
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Makoto Yoneya, H. J. C. Berendsen
専門分野: Equations of state, phase equilibria, and phase transitions.
1994 年 63 巻 3 号 p.
1025-1030
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
Preliminary results are presented on molecular dynamics simulations of the chiral nematic phase of (+)-4-(2''-metyl butyl)-4'-cyanobiphenyl. In this study, a molecular chirality is introduced by detailed atomic modeling. To treat helical structures of the chiral nematic phase, a new twisted simulation cell is introduced. The results show that the system with the twisted simulation cell gives a better fit and a lower potential energy than with an ordinary rectangular cell.
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Hiroshi Orihara, Shigeharu Hashimoto, Yoshihiro Ishibashi
専門分野: Equations of state, phase equilibria, and phase transitions.
1994 年 63 巻 3 号 p.
1031-1035
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
The D-E hysteresis loop of ferroelectrics is theoretically studied on the basis of the extended Avrami theory. If the sideway velocity depends only on the instant value of the applied field, the volume fraction of the reversed area is expressed as q(E)=1-exp, (-f
-d{Φ}(E)), where f and d are, respectively, the frequency of the applied field and the growth dimension of domains, and {Φ} is a function of E. This result is obtained irrespective of the waveform of the applied field and the field dependence of the sideway velocity, if the nucleation event is deterministic. For the stochastic nucleation due to thermal fluctuation, on the other hand, the above result is modified as q(E)=1-exp, (-f
-(d+1){Φ}(E)). The effect of the delay of wall motion is also discussed.
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Takafumi Miyanaga, Takashi Fujikawa
専門分野: Thermal properties of condensed matter.
1994 年 63 巻 3 号 p.
1036-1052
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
Temperature dependence of Debye-Waller factor in EXAFS, EELS and ARXPS is calculated for one-dimensional models on the basis of first principle quantum statistical method developed in the previous paper I. In contrast to diffraction Debye-Waller factors for crystal we have no need to worry about the divergence for these thermal factors in one- and two-dimensional phonon systems. We consider anharmonic Morse potential as nearest neighbor interaction. We take up to quartic term into account and estimate up to fourth order cumulants for both monatomic and diatomic chains in wide temperature range from low temperature in which quantum effect is important, to high temperature in which classical approximation works. Characteristic features of the contributions from optical and acoustic modes are discussed in the diatomic model chain. The result obtained here give us clear physical insights of those thermal factors.
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Sayumi Hirose, Masao Kamada
専門分野: Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties).
1994 年 63 巻 3 号 p.
1053-1058
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
The time response of excited-state potassium desorption from KCl and KBr was investigated with undulator radiation pulses. It was found that the decay curve of the optical emission from desorbed excited-state potassium atoms consists of two components, and that the fast component is several orders of magnitude faster than the existing results of time response for ground-state alkali atoms. It is suggested that the fast desorption of excited-state alkali atoms may be interpreted in terms of lattice instability due to electronic excitation in the surface layer, while a slow one originates from the thermal instability of surface defects.
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Hiroshi Shimahara
専門分野: Electron states in condensed matter.
1994 年 63 巻 3 号 p.
1059-1070
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
Spin-fermion model, or a generalized Kondo lattice model, in the phase where the localized spins are antiferromagnetically ordered, is studied. We obtain the bound state wave function of a single fermion and a single magnon with corrections of spin polaron analogous to the ordinary polaron, under some simplifying conditions analogous to Cooper's problem of the superconductivity. It is found that each fermion-magnon bound state extends over the whole space unlike the localized bound state in the single impurity Kondo model. It is also shown that there exists a finite critical value of the Kondo coupling for the bound state formation in the presense of the three dimensional interactions. We discuss the instability of the fermi surface.
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Masatake Yamaguchi, Setsuro Asano
専門分野: Electron states in condensed matter.
1994 年 63 巻 3 号 p.
1071-1080
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
The electronic structures of GdCo
5, GdFe
12, GdFe
12N, Gd
2Fe
17, and Gd
2Fe
17N
3 have been calculated self-consistently by full-potential linearized augmented plane wave method within the framework of the local spin density approximation. The second order crystal field parameters (A
20) at Gd-site of these compounds have been determined carefully from the calculated charge distribution. For GdCo
5, although the calculated value of A
20 is larger than experimental ones for SmCo
5, it is found that the crystal structure is very suitable for producing the large negative value of A
20. For the other compounds, the calculated values of A
20 except for GdFe
12 are also larger than experimental ones. The trend of the increase of A
20 by introducing nitrogen is, however, in agreement with experimental results. In RFe
11Ti and R
2Fe
17 (R=rare earth), the increase of the magnetocrystalline anisotropy energy by introducing nitrogen can be understood from the increase of the asphericity of charge distribution around R ion due to the bonding state between R ion and nitrogen.
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Makoto Kuwabara, Yoshiyuki Ono
専門分野: Electronic transport in condensed matter.
1994 年 63 巻 3 号 p.
1081-1089
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
In order to estimate the mobility of a charged soliton in polyacetylene, the dynamics of a soliton in an electric field is numerically investigated in the presence of a phenomenological damping of the lattice motion. Except for the damping term in the equation of motion for the lattice displacements, the dynamics is assumed to be determined by Su, Schrieffer and Heeger's model. It is shown that a Drude-type treatment of the soliton motion is applicable. The mobility is found to be μ =88.9, cm
2/Volt· sec, and the conductivity is estimated to be σ =7.54× 10
3, Ω
-1, cm
-1 on the assumption that the concentration of the solitons is one per 100 carbon atoms. The present result is compatible with experimental data in the non-magnetic regime.
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Katsuichi Tankei, Mitsuhiro Ikegami, Yosuke Nagaoka
専門分野: Electronic transport in condensed matter.
1994 年 63 巻 3 号 p.
1090-1103
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
The conductance fluctuations in mesoscopic quantum wires at zero temperature are studied by using the tight binding model and the transfer matrix formalism with the Landauer formula. The numerical calculations for the conductance g (scaled by e
2/h) are carried out for the overall range from the ballistic to the localized regime, and it is found numerically that a relation between the averaged conductance ‹ g› and the conductance fluctuation δ g is described by the single parameter near the ballistic regime and also near the localized regime. In the ballistic regime, we find analytically that δ g/M is proportional to (1-‹ g› /2M), which agrees well with the result of the numerical calculations (M being the channel number). By using the conductance formula due to the resonant tunneling, we discuss the behavior of the conductance near the localized regime, and find analytically that the ratio (δ g)
2/‹ g› tends to the value 0.5 as ‹ g› → 0, which is consistent with the numerical result.
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Kenji Ishida, Yoshio Kitaoka, Kunisuke Asayama, Kazuo Kadowaki, Takash ...
専門分野: Superconductivity.
1994 年 63 巻 3 号 p.
1104-1113
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
The normal and superconducting properties in single crystal Bi
2Sr
2CaCu
2O
8 (Bi2212) with T
c=86, K have been investigated by systematic measurements of the
63Cu Knight shift,
63K(T) and the nuclear-spin-lattice relaxation time, T
1. In the normal state, the T-dependences of
63K(T) and (T
1T)
-1 in Bi2212 share similar magnetic behaviors to the underdoped systems such as oxygen deficient YBa
2Cu
3O
6+x and YBa
2Cu
4O
8, namely,
63K(T) decreases with lowering temperature and
63(T
1T)
-1 has a peak above T
c. However, from the analyses of the anisotropy of 1/T
1 and the hyperfine field, Bi2212 is found to belong to the slightly over-doped region as in Tl
2Ba
2CuO
6+x and TlSr
2CaCu
2O
8-x. In the superconducting state, the finding of T
1T=const. law far below T
c has revealed that the superconductivity is in a gapless regime, accompanied by the finite density of states at the Fermi level.
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Mikio Koyano, Manabu Suezawa, Hajime Watanabe, Masasi Inoue
専門分野: Magnetic properties and materials.
1994 年 63 巻 3 号 p.
1114-1122
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
Magnetizations and ac magnetic susceptibilities at low magnetic fields using a SQUID magnetometer have been measured for spin-glass (SG; x=0.1 and 0.2) and cluster-glass (CG; x=1/4 and 1/3) phases of Fe
xTiS
2 over the frequency range 0.5--100, Hz and temperature range 4.2--80, K. The frequency and temperature variations of the ac magnetic susceptibilities have different behaviors for SG and CG; in particular, the estimated distribution function of relaxation time g(ω, , T) for x=1/4 has a double-peaked shape. The dimensionality and criticality of the CG phases are also discussed. Monte Calro simulations using a site-percolation model with a two-dimensional triangular lattice are made by taking into account the 1st, 2nd, and 3rd nearest neighbors to obtain the percolation probability P.
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Masakazu Ito, Masaki Mito, Hiroyuki Deguchi, Kazuyoshi Takeda
専門分野: Magnetic properties and materials.
1994 年 63 巻 3 号 p.
1123-1129
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
The measurements of magnetic heat capacity and susceptibility of one-dimensional S=1 antiferromagnet (CH
3)
4NNi(NO
2)
3 (TMNIN) have been carried out in order to make comparison with the theoretical results of a quantum Monte Carlo method for the Haldane system. The results for the heat capacity, which show a broad maximum around 10, K, are well reproduced by the theory with the interaction J/k
B=-12.0± 1.0, K in the temperature range T>0.2| J| S(S+1)/k
B. The low temperature heat capacity exhibits an exponential decay with gap energy Δ/k
B=5.3± 0.2, K, which gives Δ=0.44| J|, in contrast to the linear dependence on temperature as in the case for half integer spin. The residual magnetic entropy below 0.7, K is estimated to be 0.07
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Mitsumasa Ishiwata
専門分野: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
1994 年 63 巻 3 号 p.
1130-1138
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
Recoveries after nonselective inversion of the
13C lines in a coupled
13C-
1H spin system are observed under the just-resonance irradiation to one of the
1H doublet lines. The irradiating rf field is not too strong to result in any appreciable splitting of the observed lines. Only for a line connected progressively to the stirred one, the recovery can considerably be accelerated when the rf is strong enough to partially saturate absorption of the stirred one. On the other hand, the recovery for another regressively-connected line is extremely retarded by the rf field with similar amplitudes. The contrasting changes in the recoveries are attributed to the opposite coherent and incoherent effects of the relatively strong rf field for the two connected combinations of the stirred and observed lines. These results are discussed by the use of relaxation modes in the recovery process.
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Yutaka Maniwa, Takahito Saito, Atushi Ohi, Kenji Mizoguchi, Kiyoshi Ku ...
専門分野: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
1994 年 63 巻 3 号 p.
1139-1148
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
A systematic
13C NMR experiment is reported in alkali-fullerides A
3C
60 (where A
3 is alkali-metals) between superconducting transition temperature T
c and -- 100, K. Careful
13C NMR spin-lattice relaxation time study clarified the properties of the conduction electron wave functions at Fermi surface. An upper limit of Stoner exchange parameter was estimated to be -- 3, eV/(spin-carbon), which is far from spin-wave instability criterion. Based on these studies, a variation of the density of states at Fermi level, N(E
f), with T
c was deduced. The results were analyzed in terms of McMillan formula, leading to weak or medium electron-phonon coupling constants and relevant phonon energy larger than 600, K. It was strongly suggested that the A
3C
60 superconductor is described within a framework of the conventional phonon-mediated BCS superconductivity.
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Tomozo Tomoyose
専門分野: Dielectric properties and materials.
1994 年 63 巻 3 号 p.
1149-1155
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
Static dielectric constants of Ge, Sn, and isoelectronic semiconductors are calculated by using the full f-sum rule including all possible transitions of d band electrons. The d band effect on the dielectric constant is expressed by using a newly defined D factor different from the empirical D factor introduced by Van Vechten. The new D factor is directly expressed in terms of the average band gap, the energy of the d band, and the coupling oscillator strength between valence and d bands so that it has a well defined meaning in contrast to the empirical D factor. The calculated D values well reproduce the observed dielectric constant and the effective number of valence electrons which represents the excess deviation from the usual valence electron number.
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Wenwu Cao
専門分野: Dielectric properties and materials.
1994 年 63 巻 3 号 p.
1156-1161
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
The gradient coefficients in the Landau-Ginzburg theory are crucial for quantitative description of domain walls in ferroelectrics. The magnitude of these gradient coefficients are a measure of nonlocal coupling strength of the polarization. In this paper, we intend to explain the physical meaning of these gradient coefficients in terms of lattice dynamics and give some relationships between these gradient coefficients and the dispersion surface of the soft mode. The implications for the study of over damped soft modes are also discussed.
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Katsumi Irokawa, Masaru Komukae, Toshio Osaka, Yasuharu Makita
専門分野: Dielectric properties and materials.
1994 年 63 巻 3 号 p.
1162-1171
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
Dielectric, specific heat and X-ray measurement in the single crystals of TlH
2AsO
4 were carried out in a temperature range between 80, K and 400, K, and its domain structures were observed. It was found that TlH
2AsO
4 is ferroelastic below 391, K (T
I) with the spontaneous strain x
5S=4.2× 10
-2 at 293, K. TlH
2AsO
4 has two distinct domain structures at room temperature; one is the domain structure with the (100) and/or (001) domain boundaries which disappears above T
I and the other is the structure with the (201) domain boundary which has no relation with the phase transition. The crystal belongs to a monoclinic system with the space group P2
1/a in the room temperature phase and an orthorhombic system with the space group Pcan above T
I. It is suggested that the ferroelastic phase transition at T
I may be caused by an instability of acoustic B
2g mode.
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Chikara Sugiura, Hiroyuki Yamasaki, Takashi Shoji
専門分野: Optical properties and condensedmatter spectroscopy and other interactions of matter with particles and radiation.
1994 年 63 巻 3 号 p.
1172-1178
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
The Cu Lα emission spectra in fluorescence from CuS and Cu
2S are measured with a two-crystal vacuum spectrometer equipped with beryl crystals. The measured spectra are composed of a prominent peak and its high-energy structure. They are compared with the S L
2, 3 emission, S Kβ emission, Cu L
3 absorption and S K absorption spectra reported previously to obtain information about the electronic structures of the copper sulfides. It is shown that the valence bands are composed of three parts: The upper part consists of the Cu 3d states with considerable contribution of the S 3p and 3s characters, while the middle part consists of the S 3p states with small contribution of the Cu 3d and S 3s characters and the lower part arises from the S 3s states. In addition, it is shown that the hybridization between the Cu 3d and S 3p or 4p orbitals is fairly large in the lower part of the conduction band of CuS.
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Sadatsugu Muto, Serng–Yerl Park, Shin Imada, Katsuhiko Yamaguchi ...
専門分野: Optical properties and condensedmatter spectroscopy and other interactions of matter with particles and radiation.
1994 年 63 巻 3 号 p.
1179-1185
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
The magnetic circular dichroisms (MCD) in the photoabsorptions by Eu, Gd, Tb, Dy, and Ho thin films were measured in the 4d-4f excitation region. The extended MCD signals were observed except for Eu and Gd both in the lower and the higher photon energy regions with the opposite signs, indicating that the interference between the 4d-4f excitation and the 4f-ε l excitation is more dominant than the 4f-ε l potential barrier effect in heavy rare earths. The observed MCD data are in fair agreement with theoretical calculations except the intensity of the extended MCD and disappearance of some components of the multiplets.
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Satoshi Takeuchi, Ryo Sugihara, Koichi Shimoda
専門分野: Electromagnetic technology.
1994 年 63 巻 3 号 p.
1186-1193
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
It is analytically shown that the longitudinal electric field of a Gaussian laser beam in vacuum accelerates an electron to an ultra-relativistic energy. The most favorable electron is accelerated in a length of twice the Rayleigh range. It is found that the ultimate energy increment of the electron with a single laser beam is given by the product of transverse field intensity and the beam waist. Also stability of the electron orbit and the trapping condition are discussed. The gain can be of the order of 100, MeV per single stage and then a multi-stage acceleration enables TeV-order-acceleration in a length of a few kilometers with the present state of the art.
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Tetsuya Matsuno, Yukiko Kikkawa, Masahiro Iguchi, Kiyoshi Toko, Kaoru ...
専門分野: Biophysics.
1994 年 63 巻 3 号 p.
1194-1204
発行日: 1994/03/01
公開日: 1999/10/01
ジャーナル
認証あり
Responses to periodic signals in the oscillator network are studied numerically. The network used here is globally coupled oscillators with distributed natural frequencies of the oscillatory elements. The ability of the temporal-pattern recognition in the system is studied using the learning rule which changes the distribution of the natural frequencies. It is found that the coherency representing the order of the system exhibits the periodic and complex behaviors. The periodic response of the coherency is observed in the case where the input signal is similar to the learned signal. The behavior of the coherency becomes complex; i.e., the number of the degrees of freedom of the behavior increases with the decrease in the similarity of the input signal to the learned signal. Moreover, the long transient process is observed after turning off the input.
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