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Iwao Hosokawa, Shin–ichi Oide, Kiyoshi Yamamoto
Subject area: Mathematical methods in physics.
1996 Volume 65 Issue 4 Pages
873-875
Published: April 01, 1996
Released on J-STAGE: October 01, 1999
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A trinomial generalized Cantor set model is proposed to precisely predict the singularity spectrum f(α ) of dissipation measure in isotropic turbulence on the basis of the data of turbulence at the fully-developed state obtained by our recent direct numerical simulations on grids of 128
3 and 512
3. This model can be extended to reasonably predict the expectable negative parts of f(α ) by change of parameters.
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E. V. Doktorov, S.Yu. Sakovich, R. A. Vlasov
Subject area: Mathematical methods in physics.
1996 Volume 65 Issue 4 Pages
876-878
Published: April 01, 1996
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Soliton solutions are obtained for the modified Manakov equations which are the integrable version of equations proposed recently by Hisakado, Iizuka and Wadati to describe the femtosecond pulse propagation in a birefringent optical fiber.
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Takeshi Kawabe, Yoshiro Kondo
Subject area: Mathematical methods in physics.
1996 Volume 65 Issue 4 Pages
879-882
Published: April 01, 1996
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The mean laminar length of intermittency generated by the dynamical equation x
n+1=(1+ε)x
n+x
nz obeys the scaling law ‹ N › ∝ ε
-γ, where γ is related to the reinjection probability through a reinjection mapping function (1-x)^m and is approximated by γ=1-1/m(z-1). This result is ascertained by numerical simulations, and for m=1 it is in agreement with the result for the random uniform reinjection probability in type-III intermittency. It is also used not only to classify the intermittent chaos but also to determine the scaling law for the mean laminar length from the analyses of the return map which is experimentally or theoretically provided.
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Mikiko Roji, Seiji Miyashita
Subject area: Statistical physics and thermodynamics.
1996 Volume 65 Issue 4 Pages
883-886
Published: April 01, 1996
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We study how the ferromagnetic order in the XXZ Heisenberg model on a ladder lattice is destroyed by antiferromagneticbonds between chains. It is found that a critical value of J
AF existsin the Ising-like Heisenberg models.Anisotropy dependence of the critical valuesis studied by a diagonalization method. At the critical point, the energy gap between the ground state and the first excited state is found to disappear in the thermodynamic limit.Below the critical value, the gap is due to the Ising-like anisotropy while it originates from the singlet pair for antiferromagnetic bonds above the critical point.
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Chikako Uchiyama, Fumiaki Shibata
Subject area: Statistical physics and thermodynamics.
1996 Volume 65 Issue 4 Pages
887-890
Published: April 01, 1996
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A systematic damping theoretical formalism is presented to give basic equations of statistical physics. Our formalism naturally yields the so-called time convolution (TC) and time convolutionless (TCL) equations both for a density matrix and for dynamical variables. The method is explicitly used to obtain equations in the Heisenberg picture (equations of motion for dynamical variables). In contrast to the existing derivation of equations of motion, the present formalism gives a systematic method for deriving these equations without specifying the projection operator. Moreover, the formalism is valid even for time-dependent Hamiltonian systems. A simple example is given to illustrate our formalism.
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Tomotoshi Nishino, Kouichi Okunishi
Subject area: Statistical physics and thermodynamics.
1996 Volume 65 Issue 4 Pages
891-894
Published: April 01, 1996
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We propose a new fast numerical renormalization group method ---the corner transfer matrix renormalization group (CTMRG) method ---which is based on a unified scheme involving Baxter's corner transfermatrix method and White's density matrix renormalization groupmethod. The key point is that a product of four corner transfermatrices coincides with the density matrix. We formulate CTMRG as a renormalization group for 2D classical models.
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Kazuo Hida
Subject area: Statistical physics and thermodynamics.
1996 Volume 65 Issue 4 Pages
895-898
Published: April 01, 1996
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The density matrix renormalization group method is generalized to one-dimensional random systems. Using this method, the energy gap distribution of the spin-1/2 random antiferromagnetic Heisenberg chain is calculated. The results are consistent with the predictions of the re- normalization group theory demonstrating the effectiveness of the present method in random systems. The possible application of the present method to other random systems is discussed.
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Yoko Kato, Masatomo Sato
Subject area: Fluid dynamics.
1996 Volume 65 Issue 4 Pages
899-901
Published: April 01, 1996
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The Charney-Hasegawa-Mima equation is a two-dimensional nonlinear equation describing geostrophic Rossby flow and plasma drift flow. An analytic solution of the equation is given which represents a stationary vortex of an elliptic boundary in a background shear flow. The solution is obtained by assuming a suitable form for the arbitrary function in the stationary equation.
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Yasuo Yoshimura, Teruo Saito, Yasuhito Kiwamoto, Yoshinori Tatematsu, ...
Subject area: The physics of plasmas and electric discharges.
1996 Volume 65 Issue 4 Pages
902-904
Published: April 01, 1996
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Axial and radial profiles of plasma potentials in the GAMMA10 tandem mirror are studied by use of an array of Langmuir probes. Application of fundamental ECRH in the plug region strongly varies the potential profiles. However, in the end region the axial potential profile normalized by the electron temperature remains nearly the same.
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Satoshi Nishimoto, Toru Moriya
Subject area: Electronic transport in condensed matter.
1996 Volume 65 Issue 4 Pages
905-907
Published: April 01, 1996
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The electrical resistivity of metallic V
2-yO
3 is calculated assuming that the antiferromagnetic spin fluctuations dominate the scattering mechanism for the conduction electrons. The spin fluctuations are described in terms of the self-consistent renormalization theory with parameter values estimated from the results of a neutron inelastic scattering experiment. The final result agrees reasonably well with the experimental results.
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Takafumi Kita
Subject area: Superconductivity.
1996 Volume 65 Issue 4 Pages
908-911
Published: April 01, 1996
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The theory of superconductivity is formulated starting from the configuration-spaceform of the Bardeen-Cooper-Schrieffer (BCS) wave function.Self-consistent equations for treating nonuniform systems are obtained.These equations have the advantage over the Bogoliubov-de Gennes equationsthat an effective condensate wave function andquasiparticle eigenstates can separately be obtained.The intrinsic orbital angular momentum density of the condensate is naturally identified in this formalism due to a manifest two-particlebound-state nature in the one-particle density matrix.
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Arata Tanaka, Takeo Jo
Subject area: Optical properties and condensedmatter spectroscopy and other interactions of matter with particles and radiation.
1996 Volume 65 Issue 4 Pages
912-915
Published: April 01, 1996
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The effect of electron doping on the wave vector averaged 3d photoemission and inverse photoemission spectra is investigated for Cu-oxide finite clusters, including the intraatomic full multipole electrostatic interactions, by means of the recursion method. It is shown, by calculations for clusters containing up to four Cu atoms, that the doping leads to an upward shift of the upper edge of the main valence band relative to the d^9 → d^8 peak and a shift of the chemical potential (μ) to the lower edge of the conduction band of undoped systems. Also the upper valence band edge changes its character from “d^9 → d^9\underline{L}” to “d
10 → d^9” with mainly xy, yz, zx and 3z^2-r^2 symmetries. The “mid-gap μ” in doped metals inferred from experimental results is interpreted as a consequence of the disregard of the shift of the valence band relative to the d^8 peak due to finite electron doping.
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Satoshi Yukawa, Macoto Kikuchi
Subject area: Other areas of research of general interest to physicists.
1996 Volume 65 Issue 4 Pages
916-919
Published: April 01, 1996
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Density fluctuations in traffic current are studiedby computer simulations using the deterministic coupled maplattice model on a closed single-lane circuit. Bycalculating the power spectral density of temporal densityfluctuations at a local section, we find that it exhibits apower law, being proportional to 1/f
1.8 wheref is the frequency, in the noncongested flow phase. Thedistribution of the headway distance h also follows apower law, being proportional to 1/h
3.0 . Thepower-law fluctuations are destroyed by the occurrence of atraffic jam.
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Taichiro Takagi
Subject area: Statistical physics and thermodynamics.
1996 Volume 65 Issue 4 Pages
921-927
Published: April 01, 1996
Released on J-STAGE: October 01, 1999
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We give an integral representation of the internal energy of the F model, a special case of the anti-ferroelectric six-vertex model.This representation is obtained naturally as a trace function of the vertex operators.We also take the critical limit of our expression and find that it reproducesLieb's result of the internal energy at T
c.
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Akihiko Osa, Tomohiko Ikuta, Kiyoshi Kawade, Hiroshi Yamamoto, Shin&nd ...
Subject area: Nuclear decay and radioactivity.
1996 Volume 65 Issue 4 Pages
928-934
Published: April 01, 1996
Released on J-STAGE: October 01, 1999
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The β
+-ray maximum energies of neutron-deficient
121, 123, 125Ba and
121--124, 126Cs isotopes were measured using single HPGe-detector method, which does not need an annihilation-photon detection system. The radioactive sources were produced by bombarding Mo targets with
32S
10+ and
35Cl
11+ ions, followed by on-line mass-separation. The analysis of the experimental β
+-ray spectra using response functions to monoenergetic positrons yielded β
+-ray maximum energies and Q-values of orbital-electron capture (Q
EC-values) in the decay of these nuclides. The present experiment has extended the Q
EC determination to
121, 123Ba isotopes in addition to improving the accuracy for the other nuclides.
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Satoru Nishikawa, Hideo Yahata
Subject area: Fluid dynamics.
1996 Volume 65 Issue 4 Pages
935-944
Published: April 01, 1996
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We report the results on the MAC numerical simulations of the Rayleigh-Benard convection for a Boussinesq fluid with the Prandtl number Pr=6 confined in a rectangular box with the aspect ratios {Γ}
x=3.0 and {Γ}
y=1.5.With increase of the Rayleigh number, the initial state with two parallel steady rolls undergoes a successive series of transitions in such a way that (i) as for the time behavior: steady \longrightarrow periodic oscillations \longrightarrow quasi-periodic with two fundamental frequencies \longrightarrow chaotic; and that (ii) as for the horizontal spatial symmetry in terms of the point group notation: C
2v \longrightarrow C
1h \longrightarrow C
1.In particular, the periodic oscillations are shown to arise from the BO2 blob instability. The results are compared with those of the experiment on water.
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Wen–Shan Duan, Ben–Ren Wang, Rong–Jue Wei
Subject area: Fluid dynamics.
1996 Volume 65 Issue 4 Pages
945-947
Published: April 01, 1996
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The solitons propagating in an infinitely long, straight, circular, inhomogeneous tube filled with viscous blood have been investigated. A theory is proposed in this paper to explain the phenomenon that the amplitude of blood pressure and wall displacement pulses decay in very small artery. The theoretical results are estimated and compared with experimental ones. The agreement between them is good.
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M. D. Calzada, A. Rodero, A. Sola, A. Gamero
Subject area: Kinetic and transport theory of fluids; physical properties of gases.
1996 Volume 65 Issue 4 Pages
948-954
Published: April 01, 1996
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The excitation kinetic of a surface wave plasma produced by microwave is not well-known. This work presents an experimental study of this kinetic in Ar plasma. The 4p, 5p and higher levels of the Ar atomic system have been studied to determine their equilibrium separation. 5p and higher levels were found that followed an equilibrium distribution but the 4p levels were underpopulated in respect to this ditribution. Then the plasma is a recombining plasma which is in partial local thermodynamic equilibrium (pLTE). Using the phase diagram that is divided in different areas by the Green and Byron criterium we have established that the 4p levels are in saturation zone and the 5p levels and higher ones are in pLTE. For our discharge positions, those nearest to the excitator are the nearest to equilibrium population, because higher electron temperature and density imply that the plasma is nearer to thermodynamic equilibrium.
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In–Sung Jang, Hiroyuki Chiba, Shinsuke Watanabe
Subject area: Kinetic and transport theory of fluids; physical properties of gases.
1996 Volume 65 Issue 4 Pages
955-959
Published: April 01, 1996
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A vortex ring in water impacting on a plane wall has been studied experimentally in the Reynolds number range of 10
4-- 10
5. As a vortex ring approaches the wall which is placed perpendicularly to the direction of propagation, the propagation speed slows down and the major radius expands. In the present Reynolds number region, rebound of a vortex ring at the wall has been observed only once or no clear rebound has been observed. The trajectory of a vortex ring near the wall deviates from that of the inviscid fluid theory whether the rebound is clearly observed or not. The major radius continues to grow and never decreases. Due to rebound or rebound-like motion, a vortex core becomes bumpy and a wavy pattern appears along a vortex core.
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Azusa Fukano, Masatada Ogasawara
Subject area: The physics of plasmas and electric discharges.
1996 Volume 65 Issue 4 Pages
960-966
Published: April 01, 1996
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Two-stream instability induced by the interaction between a proton beam and a plasma is investigated analytically in consideration of the beam deceleration by the nonlinear effect. Expression of beam deceleration is derived from a modification of the orbit of the beam particle due to the wave potential. Nonlinear dispersion relation is obtained from a set of equations which includes the term of the beam deceleration in addition to the perturbation of the beam velocity. Saturation level of the wave potential is determined from the nonlinear growth rate. Result indicates that the beam deceleration due to the nonlinear interaction provides the saturation level which is almost equal to one obtained by the analyses based on the trapping of beam particles.
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Toshio Nakayama, Masaaki Ito
Subject area: Lattice dynamics and crystal statistics.
1996 Volume 65 Issue 4 Pages
967-972
Published: April 01, 1996
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The vibration of the one-dimensional lattice of vortices in the type II superconductor is studied. The approximate solitary wave solution is obtained by slightly modifying the analysis by Toda in his nonlinear lattice. With an aid of computer simulation, we have examined the approximate solution and found that the small but finite amplitude solitary pulse propagates just like soliton, and that the large amplitude pulse propagates by self-adjusting to form a stable solitary wave in the course of time development. The interactions of solitary waves thus obtained are quite similar to those of Toda solitons.
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Kêichiro Aizu
Subject area: Equations of state, phase equilibria, and phase transitions.
1996 Volume 65 Issue 4 Pages
973-977
Published: April 01, 1996
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This paper deals with the subject of transitions from artificially incommensurately undulated prototypic phases to ferroic phases. All of the previous papers that dealt with the mentioned subject assumed parameter δ to be invariant against the prototype symmetry operations. [The meaning of δ was well explained in the paper, J. Phys. Soc. Jpn. 63 (1994) 1018.] However, cases of δ not invariant are also worthy of study. These cases are rich in diversity. The present paper selects three typical ones (referred to as case I, …, case III) and constructs theories in them (especially in cases I and II). Differences are clarified between these theories and the theory in the most typical case of invariant δ, and between these theories themselves.
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Masahito Hosino, Huzio Nakano
Subject area: Equations of state, phase equilibria, and phase transitions.
1996 Volume 65 Issue 4 Pages
978-983
Published: April 01, 1996
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SmecticA (SmA) and columnar orders competing with each other in the system of many identical rigid square pillars in perfect alignment are theoretically investigated by applying the method of symmetry breaking potential. It is found that SmA and crystalline phases appear but no columnar phase. With the increase of density the SmA ordering falls down abruptly at a certain density being accompanied with a columnar ordering, where a first order phase transition from the SmA to crystalline phases occur. Such effects as orientational fluctuation, diversity in molecular length and small system size that suppress the SmA ordering more than the columnar one are discussed to compare the present result and those previously obtained either theoretically, experimentally or computationally by other authors.
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Kêichiro Aizu
Subject area: Equations of state, phase equilibria, and phase transitions.
1996 Volume 65 Issue 4 Pages
984-987
Published: April 01, 1996
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This paper is concerned with the subject of transitions from artificially incommensurately undulated prototypic phases to ferroic phases. It is possible that such a transition generates ferroelectricity. Ferroelectricity of this category is referred to as U-ferroelectricity, when it needs to be distinguished from conventional ferroelectricity. The most important feature of U-ferroelectricity is that it vanishes when the prototypic phase becomes homogeneous. Several different types of U-ferroelectricity are possible. Only the first and simplest one of those types is dealt with in the present paper. By case study the details are clarified. For example, what term within the free energy function is responsible for the generation of ferroelectricity and in what forms spontaneous polarization and dielectric susceptibility depend on the prototype undulation are clarified.
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Koichi Sudoh, Tatsuo Yoshinobu, Hiroshi Iwasaki, Noriko Akutsu, Yasuhi ...
Subject area: Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties).
1996 Volume 65 Issue 4 Pages
988-991
Published: April 01, 1996
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Fluctuation of a single step on the vicinal surfacein thermal equilibriumis investigated by Monte-Carlo simulationfor the ASOS (absolute solid-on-solid) model.The relation W^2(y) = G(y)/ρ^2 (at large y) between the squared step width W^2(y)and the height-height correlation function G(y), which had been predicted by the capillary wave theoryfor a vicinal surface with the step density of ρ[T. Yamamoto et al.: J. Phys. Soc. Jpn. 63 (1994) 915], is confirmed by the simulation.
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Makoto Kuwabara, Akira Terai, Yoshiyuki Ono
Subject area: Electron states in condensed matter.
1996 Volume 65 Issue 4 Pages
992-999
Published: April 01, 1996
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The structure of moving nonlinear excitations in one-dimensional electron-phonon systems is studied semi-phenomenologically by using an effective action in which the width of the nonlinear excitation is treated as a dynamical variable. The effective action can be derived from Su, Schrieffer and Heeger's model or its continuum version proposed by Takayama, Lin-Liu and Maki with an assumption that the nonlinear excitation moves uniformly without any deformation except the change of its width. The form of the action is essentially the same as that discussed by Bishop and coworkers in studying the dynamics of the soliton in polyacetylene, though some details are different. For the moving excitation with a velocity v, the width is determined by minimizing the effective action. A requirement that there must be a minimum in the action as a function of its width provides a maximum velocity. The velocity dependence of the width and energy can be determined. The motions of a soliton in polyacetylene and an acoustic polaron in polydiacetylene are studied within this formulation. The obtained results are in good agreement with those of numerical simulations.
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Hajime Yamada, Tadashi Fukawa, Takayuki Muro, Yoshiki Tanaka, Shin Ima ...
Subject area: Electron states in condensed matter.
1996 Volume 65 Issue 4 Pages
1000-1004
Published: April 01, 1996
Released on J-STAGE: October 01, 1999
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We have studied the electronic structures of GdX (X: P, As, Sb, Bi) by means of the X-ray photoemission, X-ray bremsstrahlung isochromat and vacuum ultraviolet inverse photoemission spectroscopy.We have found monotonous energy shifts of the Gd 3d, 4d and 4f levels from GdP to GdBi.Such systematic energy shifts are attributed to the reduced crystal field splitting of the Gd 5d state through GdX.The occupied valence band is dominated by the X p state.The energy shifts of the valence band are found to be much different from those of the Gd-derived states, but consistently interpreted by the band calculation.
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Yuji Aoki, Tadashi Fukuhara, Hitoshi Sugawara, Hideyuki Sato
Subject area: Electron states in condensed matter.
1996 Volume 65 Issue 4 Pages
1005-1009
Published: April 01, 1996
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To investigate the 4f magnetic state of Eu
3Ir
4Sn
13, we have measured the magnetization and specific-heat below the antiferromagnetic (AF) transition temperature T
N=10, K in the magnetic field along [100] and [110] axis. The magnetic entropy approaching Rln8 indicates 2+ valence of Eu ion at low temperatures. The existence of antiferromagnetic short-range interaction above T
N is inferred from suppressed magnetic entropy at T
N. The observed nuclear specific heat is mainly attributable to Eu nucleus. The electronic specific heat coefficient γ decreases continuously with increasing field, while the magnetic specific heat is enhanced around the metamagnetic transition field of B
M=2.8, T for B//[100].
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Noriaki Hanasaki, Seiichi Kagoshima, Noboru Miura, Gunzi Saito
Subject area: Electronic transport in condensed matter.
1996 Volume 65 Issue 4 Pages
1010-1018
Published: April 01, 1996
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Quasi two-dimensional conductor α-(BEDT-TTF)_2KHg(SCN)_4 has an anomalous electronic state in the low-temperature-low-magnetic-field-low-pressure regime below 8 K, 22 T, and 5 kbar. Angle dependent magnetoresistance oscillationsin the anomalous state were measured under high pressure with the magnetic field rotated aroundtwo axes perpendicular to each other. We studied the topology of the Fermi surface below andabove the critical pressure (5 kbar) to compare the normal state with the anomalous one. In theanomalous state, we found a new series of angle dependent magnetoresistance oscillations. Inthe normal state above the critical pressure, we found a quasi one-dimensional Fermi surfaceparallel to the b
* c
*-plane. This is considered to be responsible for the Fermi surface nesting that causes the anomalous state.Electronic states are discussed in relation to possible origins of the anomalous state.
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Thomas Strutz, Tadashi Takamasu, Noboru Miura, Kenichi Imamura, Lauren ...
Subject area: Electronic structure and electrical properties of surfaces, interfaces and thin films.
1996 Volume 65 Issue 4 Pages
1019-1027
Published: April 01, 1996
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Base and collector currents have been studied in an InAlAs/InGaAs resonant-tunneling hot electron transistor at 4.2, K in pulsed magnetic fields up to 42.5, T. Base and collector currents have been found to depend strongly on the field and its orientation. For fields perpendicular to the current direction, the base/emitter current ratio increases initially with an approximate parabolic dependence and then saturates at high fields. From this magnetic field dependence, scattering processes in the InGaAs base region are discussed. Using a classical model for electron transport under a magnetic field perpendicular to the current, values for the mean free path and scattering time in the base are obtained that agree well with theoretical values for electron-electron scattering. It is shown that the magnetic field dependence of the collector current at high perpendicular fields can be explained by single barrier tunneling. A model in WKB approximation allows to determine the electron energy. Moreover, by extrapolating the high field dependence of the collector current to zero field, a ratio for ballistic transport through the base is derived.
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Yasumasa Hasegawa, Mitake Miyazaki
Subject area: Superconductivity.
1996 Volume 65 Issue 4 Pages
1028-1033
Published: April 01, 1996
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Superconductivity of quasi-one-dimensional electronsin the magnetic field is studied. The system is described as one-dimensional electrons with nofrustration due to the magnetic field. The interaction is assumed to be attractive between electrons in thenearest chains, which corresponds to the lines of nodes of the energy gap in the absenceof the magnetic field.In the mean-field approximation, the effective interaction dependson the magnetic field and the transverse momentum. As the magnetic field becomes strong, the transition temperature of the spin-triplet superconductivity oscillates, while that of thespin-singlet increases monotonically.A possibility of the observation in the quasi-one-dimensional organicsuperconductors is discussed.
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Etsuji Yamamoto, Masato Hedo, Yoshihiko Inada, Takashi Ishida, Yoshino ...
Subject area: Superconductivity.
1996 Volume 65 Issue 4 Pages
1034-1037
Published: April 01, 1996
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Single crystals of superconducting U
6Fe were grown by both thezone-melting method and the Czochralski pulling method.The upper critical field H
c2 was determined from the electrical resistivityin applied magnetic fields, and H
c2 is found to be anisotropic;13.1 T for the field along the [001] directionand 10.4 T for [110]. Anisotropy of H
c2 is well explained by the effective mass model.
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Kazuaki Iwasa, Hironobu Ikeda, Ken H. Andersen, Roger S. Eccleston
Subject area: Magnetic properties and materials.
1996 Volume 65 Issue 4 Pages
1038-1042
Published: April 01, 1996
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The magnetic excitations in two-dimensional percolating Ising-type antiferromagnets, Rb
2Co
cMg
1-cF
4 (c=0.60 and 0.70), were studied by pulsed-neutron scattering. The peaks due to Ising-cluster excitations were clearly observed far above T
N. Their intensities exist even at 5T
N and 2T
N for c=0.60 and 0.70, respectively. This reveals that the characteristic time of the spin correlation in percolating networks is much longer than that of neutrons traveling through the systems, and, therefore, the spins can provide molecular fields at the neighboring sites, even in paramagnetic regions.
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Hideki Yoshizawa, Hazuki Kawano, Yasuhide Tomioka, Yoshinori Tokura
Subject area: Magnetic properties and materials.
1996 Volume 65 Issue 4 Pages
1043-1052
Published: April 01, 1996
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A field-induced insulator-metal (I-M) transition in Pr
0.7Ca
0.3MnO
3 has been studied with neutron diffraction experiments. Over the whole temperature range, the resistivity of Pr
0.7Ca
0.3MnO
3 shows insulating behavior at zero field, but exhibits an I-M transition at around 4.0 T at 5 K. It has been established that an applied field enforces a ferromagnetic spin alignment and drives Pr
0.7Ca
0.3MnO
3 to a metallic state by actuating the double exchange mechanism and destroying the charge ordering. This I-M transition at 5 K is accompanied with a large hysteresis. By contrast, in the field dependence at 50 K, antiferromagnetic and charge-order components are gradually recovered below 2.0 T in a field-decreasing process. Furthermore, a reentrant I-M-I transition has been observed in the temperature dependence at 2.5 T.
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Yoshiki Teramura, Arata Tanaka, Takeo Jo
Subject area: Magnetic properties and materials.
1996 Volume 65 Issue 4 Pages
1053-1055
Published: April 01, 1996
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A deviation from the X-ray magnetic circular dichroism (MCD) spin sum rule, which is derived assuming well separated core spin-orbit multiplets in the final state of X-ray absorption, is calculated for the L
2, 3 edge in the magnetized Ni, Co, Fe and Mn ions on the basis of an atomic model including the full multiplet and the crystal field with O_h symmetry. Due to the Coulomb interaction between electrons, which mixes the so-called L_3 and L_2 regions with each other, it is found that the deviation can be --10 percent for the former three ions, while for Mn
2+ it amounts to more than 30 percent. A list of the deviations for various ionic states for the above elements is presented, which may serve as a correction factor in the estimation of expectation values of magnetic quantities from MCD data.
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Takuya Okabe
Subject area: Magnetic properties and materials.
1996 Volume 65 Issue 4 Pages
1056-1064
Published: April 01, 1996
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Keeping nickel, cobalt and iron in mind, we investigate the origin of the itinerant ferromagnetism.Recent experiments show that the systems should be in an intermediate coupling regime, where the band width and the interaction energy are of the same order of magnitudes. To treat such a situation, we generalize the Gutzwiller approximation.In that, we take account of the effect of the band degeneracy and the Hund's-rule coupling in addition to the on-site repulsion. In generalizing the Gutzwiller approximation to the bands with degeneracy, we introduce the intuitive way to give the required expressions.After the discussion on nickel, the condition for the incomplete ferromagnetism, observed in cobalt and iron, is argued.Phase diagrams, which show the interplay between the band shape peculiarity and the Hund's-rule coupling, are given.It is found that for the 3d-transition metal systems, both of the Hund's-rule coupling and the special feature of the density of states are necessary to explain the itinerant ferromagnetism.
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Takashi Kawashima, Akihide Oguchi
Subject area: Magnetic properties and materials.
1996 Volume 65 Issue 4 Pages
1065-1071
Published: April 01, 1996
Released on J-STAGE: October 01, 1999
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Using the 2-site CPA, we show that in the two-dimensional dopedIsing-like Heisenberg ferromagnets the dependence of the coherent exchangecouplings on the impurity concentration is the same as that ofantiferromagnets. The coherent magnetic fields and magnetic susceptibilitiesare obtained within the framework of the 1-site CPA. The magneticsusceptibilities obtained from the CPA are compared with the perturbativeresults in the low impurity concentration range.
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Kazuo Kanematsu, Naoki Ohkubo, Kazuo Itoh, Shuichi Ban, Tsuyoshi Miyaj ...
Subject area: Magnetic properties and materials.
1996 Volume 65 Issue 4 Pages
1072-1076
Published: April 01, 1996
Released on J-STAGE: October 01, 1999
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The isothermal deuterium absorption and desorption experiments, X-ray and magnetization measurements revealed four types of deuterides in YFe
2D
x, γ
1 of 3.8
2 of x<3.4, and β and amorphous of x<2.1 at room temperature. The crystal structure of all deuterides are rhombohedral. The magnetization of all deuterides are about 3.8, μ B/YFe2Dx and the Curie temperatures are 120, K for the γ 1-deuteride and 300, K for the γ 2-deuteride. The β -deuteride is always a mixture with the amorphous deuteride, and the Curie temperature of amorphous deuteride is 570, K and that of β -deuteride varies from 290, K to 400, K with increasing deuterium concentration. Mössbauer mesurements were performed and hyperfine fields of Fe were estimated for every deuterides.
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Parhat Ahmet, Melike Abliz, Rikio Settai, Kiyohiro Sugiyama, Yoshichik ...
Subject area: Magnetic properties and materials.
1996 Volume 65 Issue 4 Pages
1077-1082
Published: April 01, 1996
Released on J-STAGE: October 01, 1999
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We have measured the magnetic susceptibility and the magnetization of PrCu_2. These magnetic properties are highly anisotropic, which are mainly due to the orthorhombic crystalline electric field (CEF). The energy scheme of the 4f levels in PrCu_2 has been estimated by fitting the CEF theory to the susceptibility data. A new metamagnetism has been observed in the wide temperature range of 1.3 K to 50 K. The transition field increases almost linearlyfrom 10 T to 32 T with the increase of temperature from1.3 K to 50 K.
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Yoh Kohori, Kazuyuki Matsuda, Takao Kohara
Subject area: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
1996 Volume 65 Issue 4 Pages
1083-1086
Published: April 01, 1996
Released on J-STAGE: October 01, 1999
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We present
29Si NMR spectra, nuclear spin-lattice relaxation time, T_1, and nuclear spin echo decay time, T_2, measurements in URu_2Si_2 over the temperature range from 0.15 K to 300 K. 1/T_1 obtained with c-axis perpendicular to the external field H
ext, 1/T
1⊥, is much larger than that obtained with c-axis parallel to H
ext, 1/T
1//. Existence of large anisotropy of 1/T_1 together with the nearly isotropic
29Si hyperfine field imply that the spin fluctuations exist predominantly in the direction of the tetragonal c-axis. The temperature, T, dependence of 1/T
1⊥, // is nearly T-independent above 60 K and is proportional to T at low temperatures, which indicates the crossover from the localized state at high temperatures to the Fermi liquid state below about 60 K occurs in the electronic state of 5f electrons. 1/T_1 and 1/T_2 decrease markedly below T
N=17.5 K associated with the antiferromagnetic order. Below T
C, 1/T_1 has no coherence peak and decreases proportionally to T
3 at low temperatures, which is well described in term of an anisotropic superconducting energy gap model with line nodes. Although the decrease of Knight shift was expected in spin-singlet superconductor mediated by antiferromagnetic electron-electron coupling mechanism, no decrease of
29Si Knight shift was detected within experimental errors.
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C. J. Franco, A. S. Chaves, G. M. Ribeiro, R. Gazzinelli
Subject area: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
1996 Volume 65 Issue 4 Pages
1087-1092
Published: April 01, 1996
Released on J-STAGE: October 01, 1999
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The electron paramagnetic resonance (EPR) of the Tl
2+ center in Rb
2Cd
2(SO
4)
3 was investigated in the temperature range 10, K to 140, K. Special attention was paid to the Rb
+ site surrounded by nine oxygens. The studies show that at the cubic, → monoclinic phase transition, at 130, K, that block of oxygens rotates almost rigidly around one of the ‹ 0\bar{1}1› crystallographic axes. The angle of rotation changes abruptly at the transition temperature and increases linearly with decreasing temperature in the monoclinic phase. The spectra show no evidence for the cell multiplication observed in X-ray diffraction. Additional changes of the EPR spectra were observed at 101, K and 68, K. Between those two temperatures the spectra seem to be consistent with a triclinic symmetry. Below 68, K the spectra become more complex, which contrasts with the higher symmetry of the orthorhombic phase previously attributed to the crystal.
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Taisei Matsumoto, Simon J. Sutton, Kunihide Izumi, Hideki Miyaji, Koji ...
Subject area: Dielectric properties and materials.
1996 Volume 65 Issue 4 Pages
1093-1098
Published: April 01, 1996
Released on J-STAGE: October 01, 1999
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Dielectric constants are measured for the crystals of a polydiacetylene (PTS); dielectric anomalies are observed in the directions parallel and perpendicular to the chain axis of PTS in a temperature range including a phase transition around 195 K. The crystals of PTS show an antiferroelectric transition. We derive a Landau free energy on the basis of group theoretical analysis of both the high and low temperature phases. The anomalous dielectric behavior is discussed with the free energy.
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Hirokazu Yanagihara, Masakiyo Horioka, Shigeki Furuta, Toshihisa Yamag ...
Subject area: Dielectric properties and materials.
1996 Volume 65 Issue 4 Pages
1099-1101
Published: April 01, 1996
Released on J-STAGE: October 01, 1999
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The complex dielectric constant of Li
2Ge
7O
15 crystal has been measured in the frequency range from 0.1, GHz to 30, GHz. The relaxation type dispersion which shows a soft relaxational mode behavior has been observed near T
c. Consistency between the relaxation type dispersion of the present study and the resonant type dispersion of the soft phonon mode by Volkov et al. is examined through the comparison of the dynamic and the static properties. From the present analysis, we conclude that the soft relaxational mode is due to the overdamping of the soft phonon mode.
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Toru Shima, Masaru Kasahara, Pho Kaung, Toshirou Yagi
Subject area: Optical properties and condensedmatter spectroscopy and other interactions of matter with particles and radiation.
1996 Volume 65 Issue 4 Pages
1102-1105
Published: April 01, 1996
Released on J-STAGE: October 01, 1999
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The central peak of the Raman spectrum of ferroelectric LiH
3(SeO
3)
2 was observed as a function of temperature from 300, K to the melting point (383, K). With increasing temperature, the linewidth takes a minimum around 360, K and then shows anomalous broadening near the melting point. The temperature dependence of the linewidth is decomposed into two components; one component decreases linearly with temperature and the other one shows an anomalous increase toward the melting point. The analysis shows that the former is caused by the critical slowing down of the fluctuating electric polarizations in the ferroelectric phase and the latter by the activation of the ionic motion due to the premelting phenomena.
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Tetsuhiko Tomiki, Yoshihiro Isa, Yoshie Kadekawa, Yoshiiku Ganaha, Nag ...
Subject area: Optical properties and condensedmatter spectroscopy and other interactions of matter with particles and radiation.
1996 Volume 65 Issue 4 Pages
1106-1113
Published: April 01, 1996
Released on J-STAGE: October 01, 1999
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Optical absorption curves for nominally pure and Ce
3+ doped single crystals of Y
3Al
5O
12 (YAG) have been measured in the region of 5, eV--7, eV at 292, K, 78, K and 10, K. The parameters of the Urbach rule have been determined referring to those optical absorption curves which are believed to be the fundamental absorption tail of YAG single crystals at these temperatures, respectively. Optical absorption measurements on single crystals of YAG:Nd
3+ (the concentration [Nd
3+]
L being 0.60, atm.\have disclosed strong absorption spectra consisting of at least five Gaussian bands in the region of 5.0, eV--7.0, eV at 292, K and 78, K. These spectra have been interpreted to originate from the interconfigurational transitions 4f
3→ 4f
25d of Nd
3+ in YAG.
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Pho Kaung, Masaru Kasahara, Toshirou Yagi
Subject area: Optical properties and condensedmatter spectroscopy and other interactions of matter with particles and radiation.
1996 Volume 65 Issue 4 Pages
1114-1118
Published: April 01, 1996
Released on J-STAGE: October 01, 1999
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Temperature dependence of the ν
2 mode in mixed crystals K
3D_xH
1-x(SO
4)
2 was studied by Raman scattering from room temperature to 20, K. The ν
2 modes of both HSO
4- and DSO
4- ions are observed separately. The frequency shift of HSO
4- ion, ω (HSO
4), below T
c depends on temperature as (1-(T/T
c))
β with β =0.25± 0.05 when it is measured from the frequency at T
c. A discrete change in the frequency of DSO
4- just below T
c is observed in the mixed crystals and its origin is explained in relation to the interaction among dimers. The temperature dependence of the anomalous broadening of the linewidth above T
c is explained well by a mechanism similar to the motional narrowing effect in NMR.
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Kazuya Hayata
Subject area: Classical and quantum physics: mechanics and fields.
1996 Volume 65 Issue 4 Pages
1119-1120
Published: April 01, 1996
Released on J-STAGE: October 01, 1999
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Nobuo Suzuki, Fumitaka Matsubara
Subject area: Statistical physics and thermodynamics.
1996 Volume 65 Issue 4 Pages
1121-1122
Published: April 01, 1996
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Kazuya Hayata
Subject area: Optics.
1996 Volume 65 Issue 4 Pages
1123-1124
Published: April 01, 1996
Released on J-STAGE: October 01, 1999
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Michio Matsumoto, Satoshi Takeuchi
Subject area: Kinetic and transport theory of fluids; physical properties of gases.
1996 Volume 65 Issue 4 Pages
1125-1126
Published: April 01, 1996
Released on J-STAGE: October 01, 1999
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