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Volume 58, Issue 8
Displaying 1-50 of 55 articles from this issue
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Gildemar C. Santos1989 Volume 58 Issue 8 Pages 2609-2611
Published: August 15, 1989
Released on J-STAGE: June 01, 2007
JOURNAL RESTRICTED ACCESSIt is demonstrated that, after a change of coordinates, the cylindrical non-linear Schroedinger equation passes the Painlevé test. An oscillatory and a stationary exact solutions are found.View full abstractDownload PDF (244K) -
Masaru Sugiyama1989 Volume 58 Issue 8 Pages 2612-2614
Published: August 15, 1989
Released on J-STAGE: June 01, 2007
JOURNAL RESTRICTED ACCESSA self-consistent approximation method for an evolution equation of a probability distribution which is not far from Gaussian is proposed by using an information-theoretical quantity, that is, Kullback-Leibler’s information. One typical example is considered as an illustration. It is also shown that the results are concisely represented by the Wiener-Hermite expansion.View full abstractDownload PDF (380K) -
Osamu Sano, Takashiro Wakayama1989 Volume 58 Issue 8 Pages 2615-2618
Published: August 15, 1989
Released on J-STAGE: May 29, 2007
JOURNAL RESTRICTED ACCESSAn experimental study was made on the thermal convection in a thin vertical torus placed in a nearly uniform negative vertical temperature gradient. We analysed the flow field by several visualisation methods as well as an LDV (laser Doppler velocimeter) measurement. The critical Rayleigh number, the Rayleigh number dependence of the velocity profile of a quasi-one-dimensional flow along the loop, and the three-dimensional flows with cellular structures before the system became chaotic are shown. The existence of the cellular structures is quite different from the behaviour expected by the Lorenz model.View full abstractDownload PDF (548K) -
Yasuhito Kiwamoto, Teruo Saito, Isao Katanuma, Kazuaki Kurihara, Syoic ...1989 Volume 58 Issue 8 Pages 2619-2622
Published: August 15, 1989
Released on J-STAGE: June 01, 2007
JOURNAL RESTRICTED ACCESSA theoretical model is presented which accounts for an enhanced flux of loss-cone electrons observed when fundamental electron cyclotron resonance heating (ECRH) is applied on a magnetic slope in a tandem-mirror plasma. The essential point of the model consists in the velocity-space diffusion across densely converging heating-characteristic curves along which electrons have high mobility under strong ECRH. Remaining shortcomings in the present model are also addressed.View full abstractDownload PDF (504K) -
Kazuya Kamon, Yasuo Nishihata, Hiromitsu Naono, Hikaru Terauchi1989 Volume 58 Issue 8 Pages 2623-2625
Published: August 15, 1989
Released on J-STAGE: June 01, 2007
JOURNAL RESTRICTED ACCESSExtended X-ray absorption fine structure (EXAFS) measurements were carried out to investigate the local structure around the light atom (Mg) in dehydrated Mg(OH)2−2xOx. Using the UVSOR facility, the Mg-K edge spectra were carefully observed below and above the critical concentration of MgO, xc=0.68. The ratio between the first and the second coordination numbers, N2⁄N1, increases with the progress of dehydration in the range of x<xc and becomes nearly constant above xc, implying that the vacancy enhancement and destruction of Mg layers occur in the dehydration.View full abstractDownload PDF (344K) -
Yutaka Toyozawa1989 Volume 58 Issue 8 Pages 2626-2629
Published: August 15, 1989
Released on J-STAGE: June 01, 2007
JOURNAL RESTRICTED ACCESSWith the use of a simple adiabatic model in which an electron-hole pair can be annihilated across the band gap under local lattice distortion, we compared the radiative and nonradiative processes, and classified the relaxed excited state into five types considering their roles as recombination channels. They are: the free exciton (F), the self-trapped exciton (SI or SII) which was immune from or survived the dynamic nonradiative annihilation on its way from F, the nonluminescent Frenkel defect (SIII), and the unstable state (U), corresponding to the increasing ratio of the exciton lattice relaxation energy to the band gap. The results are not only consistent with the general trend of available experiments on a variety of materials, but will also be useful for the prediction of relevant features of known and unknown materials.View full abstractDownload PDF (560K) -
Kiichi Okuda, Satoru Noguchi, Yasuo Takigawa, Yoshio Murashita, Junji ...1989 Volume 58 Issue 8 Pages 2630-2633
Published: August 15, 1989
Released on J-STAGE: June 01, 2007
JOURNAL RESTRICTED ACCESSThe valence of Ce in α-Ce3Al was investigated by means of XPS measurements in a temperature range from 300 K to 3.7 K. Below 120 K, the presence of Ce4+ was detected, and its relative intensity I(Ce4+⁄Ce3+) increased with decreasing temperature. An anomaly of the magnetic susceptibility near 100 K was successfully explained by taking account of the valence change.View full abstractDownload PDF (440K) -
Shingo Katsumoto, Fumio Komori, Naokatsu Sano, Shun-ichi Kobayashi1989 Volume 58 Issue 8 Pages 2634-2637
Published: August 15, 1989
Released on J-STAGE: May 29, 2007
JOURNAL RESTRICTED ACCESSWe report variable range hopping conduction (VRHC) in the insulating phase near the metal-insulator transition in Al0.3Ga0.7As:Si. In the VRHC region, the temperature dependence of the resistivity obeys Efros and Shklovskii’s T1⁄2 law rather than Mott’s T1⁄4 law. This means the Coulomb repulsion effect is important to the transport in this system. These results and those of dielectric constant measurements reported previously are explained by Efros and Shklovskii’s theory. On the other hand, the magnetoresistance in VRHC is negative; no clear theoretical explanation has been found for this.View full abstractDownload PDF (544K) -
Kenji Ishida, Takayuki Kondo, Yoshio Kitaoka, Kunisuke Asayama1989 Volume 58 Issue 8 Pages 2638-2641
Published: August 15, 1989
Released on J-STAGE: June 01, 2007
JOURNAL RESTRICTED ACCESSNuclear quadrupole resonance (NQR) of Cu in (La1−xSrx)2CuO4 system (0.075≤x≤0.15) has been performed where the system is transformed from the high-Tc superconducting to the normal metallic state. The NQR frequency increases and the spectrum is broadened with increasing x. The nuclear spin-lattice relaxation rate 1⁄T1 shows a remarkable distribution for more than x=0.125. For the nonsuperconducting compound of x=0.15, each component of 1⁄T1 is suppressed as compared to that in the superconducting compound of x=0.075 which is strongly enhanced by antiferromagnetic spin correlation of Cu-d hole, and is found to obey the Korringa relation, T1T=const. from 1.4 to 90 K. This dramatic change of 1⁄T1 is accompanied by the disappearance of Tc. It is concluded that the superconductivity is realized with the background of the A.F. spin correlation.View full abstractDownload PDF (464K) -
Yoshikazu Suzumura1989 Volume 58 Issue 8 Pages 2642-2645
Published: August 15, 1989
Released on J-STAGE: June 01, 2007
JOURNAL RESTRICTED ACCESSThe effect of nonmagnetic impurities on the NMR relaxation time, T1, of quasi-one-dimensional superconductors with anisotropic order parameters has been studied based on the previous calculation of the thermodynamic quantities. The relaxation rate, T1−1, is examined as a function of both temperature and the impurity concentration by taking account of the vertex correction for the impurity scattering. It is shown that the enhancement of T1−1 near the transition temperature exists only for a small concentration of impurity. By the increase of impurity, the value of T1−1 at absolute zero temperature increases continuously from zero and becomes equal to that of the normal state at the critical concentration.View full abstractDownload PDF (436K) -
Jun Akimitsu, Hiroshi Sawa, Tamaki Kobayashi, Hideo Fujiki, Yasusada Y ...1989 Volume 58 Issue 8 Pages 2646-2649
Published: August 15, 1989
Released on J-STAGE: June 01, 2007
JOURNAL RESTRICTED ACCESSA neutron scattering study on Nd2CuO4, a mother material of the electron-doped superconductor (Nd1−xCex)CuO4−y, was carried out. Reentrant magnetic phase transitions associated with spin reorientation of antiferromagnetic ordering were observed. La2NiO4-type order was stabilized in the range 80 K\lesssimT\lesssim250 K and at T\lesssim40 K. Between 40 K\lesssimT\lesssim80 K, La2CuO4-type order was realized. Diffuse scattering due to the two-dimensional spin fluctuation was also observed at around T\simeq250 K.View full abstractDownload PDF (404K) -
Masatoshi Imada1989 Volume 58 Issue 8 Pages 2650-2653
Published: August 15, 1989
Released on J-STAGE: May 29, 2007
JOURNAL RESTRICTED ACCESSThe possibility of chiral symmetry breaking in quantum spin systems is examined by the extrapolation of exactly diagonalized results on finite lattices in the ground state. Both on the triangular and the square lattice, linear dependence of squared chirality on the inverse linear size in the free boundary condition strongly suggests that the correlation of chirality defined by S1·(S2×S3) is short-ranged in the thermodynamic limit, which also leads to the absence of the flux state.View full abstractDownload PDF (348K) -
Shuichi Kawamata, Hideo Iwasaki, Norio Kobayashi, Toshiaki Mitsugashir ...1989 Volume 58 Issue 8 Pages 2654-2657
Published: August 15, 1989
Released on J-STAGE: May 29, 2007
JOURNAL RESTRICTED ACCESSThe electrical resistivity and magnetization of UPdGe have been measured in magnetic fields up to 60 kOe. We have found for the first time that the localized U moments enter a ferromagnetic state below 33 K following the spin-periodic ordered state below 55 K. A decrease of the resistivity is observed at both magnetic phase transitions. In the spin-periodic state, the large negative magnetoresistance accompanied by metamagnetismlike transition is observed. The ferromagnetic order reduces the electrical resistivity to a greater extent than the spin-periodic order. The results indicate that the effect of the magnetic superzone, as well as the effect of the magnetic scattering, is important when the magnetic ordering changes.View full abstractDownload PDF (548K) -
Shinji Wada, Tatsuo Kobayashi, Makoto Kaburagi, Kazuyuki Shibutani, Ri ...1989 Volume 58 Issue 8 Pages 2658-2661
Published: August 15, 1989
Released on J-STAGE: May 29, 2007
JOURNAL RESTRICTED ACCESSThe magnetic properties in the La2NiO4+δ system have been investigated by 139La nuclear quadrupole resonance (NQR). The structure or the NQR spectrum at 1.4 K was found to depend sensitively on annealing procedures of the compounds, and therefore on δ. A well-characterized spectrum was obtained for samples oxygenated (δ≥0.066) and deoxygenated (δ∼0.022) with different structures, exhibiting the existence of the internal magnetic fields Hmt of ∼17.8 kOe nearly parallel to the basal Ni–O plane and ∼19.3 kOe perpendicular to the plane. The strength of Hmt at the La site was significantly large when compared with that of ∼1 kOe in La2CuO4 and could not be explained simply by the dipole field caused by Ni spin moments.View full abstractDownload PDF (516K) -
Tatsuo Kobayashi, Shinji Wada, Yoshio Kitaoka, Kunisuke Asayama1989 Volume 58 Issue 8 Pages 2662-2664
Published: August 15, 1989
Released on J-STAGE: May 29, 2007
JOURNAL RESTRICTED ACCESSNuclear spin-lattice relaxation times T1 of 139La in high-TC superconductor (La1−xSrx)2CuO4 (x=0.075, 0.10) have been measured in zero field. T1−1 in the superconducting state decreases rapidly, indicating a superconducting energy gap formation, but no signs of T1−1 enhancement are observed just below TC. T1−1 in the normal state shows slightly stronger temperature dependence than that expected from the Korringa relation (T1T=const.) observed in a highly Sr-doped, nonsuperconducting compound with x=0.15.View full abstractDownload PDF (352K) -
Shin Imada, Takeo Jo1989 Volume 58 Issue 8 Pages 2665-2668
Published: August 15, 1989
Released on J-STAGE: June 01, 2007
JOURNAL RESTRICTED ACCESSThe Ce 3d and 4d core X-ray photoemission spectra (3d and 4d XPS) of Ce compounds are studied based on the impurity Anderson model considering atomic multiplets arising from electron-electron interaction. We make a consistent analysis of 3d and 4d XPS of trivalent Ce compounds CeF3, CeCl3 and Ce2O3, which can only be made by considering the atomic multiplets. We also apply the approach to the interpretation of the spectra of mixed valent Ce systems Ce–Ni compounds and CeO2. We show that the analysis of the multiplet structure gives information about many-body electronic states of the system.View full abstractDownload PDF (532K) -
Arisato Ejiri, Kazumichi Nakagawa1989 Volume 58 Issue 8 Pages 2669-2672
Published: August 15, 1989
Released on J-STAGE: May 29, 2007
JOURNAL RESTRICTED ACCESSOptical absorption spectra of excitons in very thin alternating KCl–KBr multilayer structures are studied for the first time. Instead of KBr bulk-exciton peaks, new sharp spikes having a much steeper rise and located above the respective bulk-exciton peak are observed on these spectra. The spikes are interpreted with terms of quantum well exciton confined in the thin KBr layer. It is also suggested that mixture formed at inferfaces of the two materials plays important roles in the quantum confinements.View full abstractDownload PDF (620K) -
Michihiro Kobayashi, Mitsugu Yamanaka, Mikiya Shinohara1989 Volume 58 Issue 8 Pages 2673-2676
Published: August 15, 1989
Released on J-STAGE: May 29, 2007
JOURNAL RESTRICTED ACCESSThe pressure dependence of absorption spectra in 3C-SiC crystals has been studied up to 14 GPa at room temperature by using a diamond anvil cell. The pressure derivative of the fundamental gap between Γv and Xc band extrema is found to be −1.9 meV/GPa, the absolute value of which is anomalously small, in contrast with the values usually observed for Γv−Xc (or Δc) gaps in the diamond and zinc-blende structure semiconductors or insulators. Luminscence spectra measured at 1.8 K reveal that the binding energy of excitons trapped by donors increases drastically at pressures higher than 4 GPa.View full abstractDownload PDF (468K) -
Masao Nomura1989 Volume 58 Issue 8 Pages 2677-2686
Published: August 15, 1989
Released on J-STAGE: June 01, 2007
JOURNAL RESTRICTED ACCESSThe 6−j symbol (the Racah coefficient) is described in a form of linear combination of 3−j symbols (Clebsch-Gordan coefficients). Deduction is based on the quasi-spin formalism combined with the state operator formalism. The result is used to express the 9−j symbol, expanded usually in terms of three 6−j symbols, as a weighted sum over two 3−j symbols. The obtained expressions facilitate rapid evaluation of the 6−j and the 9−j symbols. An asymptotic expansion of the 9−j symbol is discussed.View full abstractDownload PDF (928K) -
Akira Nakamura1989 Volume 58 Issue 8 Pages 2687-2693
Published: August 15, 1989
Released on J-STAGE: June 01, 2007
JOURNAL RESTRICTED ACCESSWe consider the 3+1 dimensional Toda equation Δ log Vn−Vn+1+2Vn−Vn−1=0 where Δ≡(∂⁄∂x)2+(∂⁄∂y)2+(∂⁄∂z)2. The boundary condition is molecule type which is Vn=0 at finite n corresponding to both ends of the finite chain. We take the form of the solution to be Vn(x, y, z)=Vn(r, θ, φ)=r−2Vn(θ, φ) where r, θ and φ are usual spherical coordinates. We have found explicit multiple soliton solutions for Vn(θ, φ), which correspond to the superpositions of arbitrary number of axially symmetric solutions with each symmetry axis directing to arbitrary different directions.View full abstractDownload PDF (560K) -
Masao Nomura1989 Volume 58 Issue 8 Pages 2694-2704
Published: August 15, 1989
Released on J-STAGE: June 01, 2007
JOURNAL RESTRICTED ACCESSA trigonometric function parametrization of Yang-Baxter (Y-B) relations is described in terms of n−j symbols of suq(2), a deformation of su(2). The formalism starts with deduction of the Y-B relation for the IRF (interaction round a face) model of suq(2) from a general operator relation for the vertex model. The relation obtained for the IRF model is transformed into the Y-B relation for the vertex model using the property that the 3−j symbol is an asymptotic limit of the 6−j symbol. A class of very general solutions to Y-B equations is also presented. This solution of the IRF model with infinite rapidity parameters is linked to a symmetry of the 12−j symbol of the second kind.View full abstractDownload PDF (1164K) -
Ryogo Hirota1989 Volume 58 Issue 8 Pages 2705-2712
Published: August 15, 1989
Released on J-STAGE: June 01, 2007
JOURNAL RESTRICTED ACCESSWe propose the following integral equation for solving the BKP equations
K(x, z)+F(x, z)−∫−∞xDyK(x, y)·F(y, z) dy=0
where F(x, y) satisfies the linear differential equation
(Remark: Graphics omitted.),
with the conditions F(x, y)=−F(y, x) and F(x, −∞)=0.
The τ-function, solution to the BKP equations in the bilinear form is related to the solution K(x, y) of the integral equation through the relation
(Remark: Graphics omitted.).
The integral equation plays the same role as that of the Gel’fand-Levitan integral equation used in solving the KP (Kadomtsev-Petviashvili) equation.View full abstractDownload PDF (620K) -
Yoko Hase, Ryogo Hirota, Yasuhiro Ohta, Junkichi Satsuma1989 Volume 58 Issue 8 Pages 2713-2720
Published: August 15, 1989
Released on J-STAGE: June 01, 2007
JOURNAL RESTRICTED ACCESSIt is shown that the Mel’nikov equations can be considered as a system of the KP equation, its Bäcklund transformation and the two-dimensional Toda equation. Soliton solutions of bright- and dark-types for the Mel’nikov equations are derived from the Wronskian solutions of the system. The relation of solutions between the Mel’nikov equations and a system comprised of the nonlinear Schrödinger equation coupled to the Boussinesq equation is also briefly mentioned.View full abstractDownload PDF (724K) -
Susan Tolman, Paul Meakin, Mitsugu Matsushita1989 Volume 58 Issue 8 Pages 2721-2726
Published: August 15, 1989
Released on J-STAGE: May 29, 2007
JOURNAL RESTRICTED ACCESSLarge-scale computer simulation results are presented for the cluster-size distributions Ns in the incremental growth of on-lattice and off-lattice DLA clusters in the spatial dimensions d=2–5. The clusters are first grown to a size of s1 particles and additional s2 particles are added. Then the number Ns of clusters or “trees” of size s in the incremental growth consisting of the last s2 particles added is obtained to investigate the s-dependence of Ns. It is found that Ns can be approximately described by the power-law form, Ns∼s−τ with the apparent values of the exponent τ≅1.65, 1.76, 1.70 for hypercubic lattice DLA and τ≅1.68, 1.77, 1.71 for off-lattice DLA in d=2–4, respectively. A value of about 1.66 was obtained for τ from five-dimensional off-lattice simulations. These exponents are related to the fractal dimensionality of the old growth/new growth interface.View full abstractDownload PDF (608K) -
Masakazu Ichiyanagi1989 Volume 58 Issue 8 Pages 2727-2740
Published: August 15, 1989
Released on J-STAGE: June 01, 2007
JOURNAL RESTRICTED ACCESSBy means of the time-smoothing method developed in the previous papers of this series, the quantum kinetic equation is derived from the principles of statistical mechanics. In this paper, we avoid the BBGKY hierarchy; instead we use the Liouville-von Neumann equation for the time-smoothed density matrix. The Boltzmann distribution function is defined in terms of this time-smoothed density matrix. The present scheme may be applied to strong-coupling systems even if they are not in near equilibrium.View full abstractDownload PDF (1548K) -
Kazuhiro Satoh1989 Volume 58 Issue 8 Pages 2741-2757
Published: August 15, 1989
Released on J-STAGE: June 01, 2007
JOURNAL RESTRICTED ACCESSNumerical studies are made out the behavior of a random neural network in which each neuron is coupled to a certain number of randomly chosen neurons. Such a random-net serves as a simple model for an elemental sub-network of the cortex. Neurons are regarded as binary decision elements, and they synchronously update their values in discrete time steps according to a deterministic equation (the McCulloch-Pitts model). It is found that each random-net containing one hundred neurons has only a few kinds of characteristic modes of excitation. Periods of these modes are usually less than ten steps when the number of connections per neuron is two to five. For the random-net containing one thousand neurons, an excited mode is practically aperiodic. When the refractory period is introduced, however, a nearly periodic oscillation takes place in the activity of the network.View full abstractDownload PDF (1600K) -
Yoshikazu Fujii, Kouji Sueoka, Kenji Kimura, Michi-hiko Mannami1989 Volume 58 Issue 8 Pages 2758-2766
Published: August 15, 1989
Released on J-STAGE: June 01, 2007
JOURNAL RESTRICTED ACCESSCharge state distributions of He ions transmitted through self-supporting SnTe and Au single crystals with atomically clean surfaces are measured for the energy range 0.5–2.0 MeV. Anomalous reduction of He+ fraction is observed at planar channeling conditions. This is explained by the position dependent electron-loss and -capture probabilities of channeling He ions calculated from the classical Bohr and Bohr-Lindhard models. The effect of surface reconstruction on the charge state distribution is also discussed.View full abstractDownload PDF (1020K) -
Osamu Inoue1989 Volume 58 Issue 8 Pages 2767-2778
Published: August 15, 1989
Released on J-STAGE: June 01, 2007
JOURNAL RESTRICTED ACCESSDependence of flow features in two-dimensional (2D) vortex simulation on time-integration scheme is studied. Three types of scheme are applied to a flow past an impulsively started flat plate set normal to the freestream; the first-order Euler scheme, the second-order Adams-Bashforth scheme and the fourth-order Runge-Kutta scheme. Calculated results are compared with experiments. The Adams-Bashforth scheme and the Runge-Kutta scheme prove to give flow features close to each other, while the Euler scheme gives somewhat different results from the others. As to the temporal growth of separation bubbles, the Euler scheme gives the best agreement with experiments. Effects of parameters such as the numerical core-radius and the time-step are also studied.View full abstractDownload PDF (1100K) -
Hitoshi Kikuchi, Hakaru Ueno, Katsunori Saito, Shoichi Shiina1989 Volume 58 Issue 8 Pages 2779-2788
Published: August 15, 1989
Released on J-STAGE: June 01, 2007
JOURNAL RESTRICTED ACCESSThe pitch modulation on an l=1 torsatron field leads to the improvement of the confinement properties due to the formation of a local magnetic well, the reduction of the field ripple and the increase of the rotational transform. The pitch-modulated l=1 torsatron has the simplest coil structure and generates a compact helical magnetic axis configuration with a much smaller excursion amplitude than the coil radius. Here, the vacuum configuration and the finite beta equilibrium of this system are described.View full abstractDownload PDF (976K) -
Ahmed E. Radwan1989 Volume 58 Issue 8 Pages 2789-2793
Published: August 15, 1989
Released on J-STAGE: June 01, 2007
JOURNAL RESTRICTED ACCESSThe electrodynamic (in-) stability of a self-gravitating dielectric fluid cylinder ambient with dielectric medium is discussed. A general dispersion relation valid to all (axisymmetric and non-axisymmetric) modes of disturbance is derived. The model is gravitationally stable to all non-axisymmetric disturbance modes while to axisymmetric mode it is so if the longitudinal wavenumber normalized with respect to the radius of the fluid cylinder is equal to or greater than 1.0668 and vice versa. The electrodynamic force has always stabilizing effects to all modes of disturbance for all wavelengths whatever the electric field intensity strength. As the latter is increasing the gravitational instability is decreasing and above a certain value of the electric field intensity the gravitational instability is completely suppressed and stability sets in. These analytical results are confirmed numerically.View full abstractDownload PDF (528K) -
Reiji Sugaya1989 Volume 58 Issue 8 Pages 2794-2804
Published: August 15, 1989
Released on J-STAGE: June 01, 2007
JOURNAL RESTRICTED ACCESSGeneral expressions of the matrix elements for nonlinear resonant wave-wave interactions of electromagnetic and electrostatic waves in a homogeneous magnetized plasma are derived from the Vlasov-Maxwell equations. The kinetic wave equations obtained for electromagnetic waves are represented by three-order tensors in the rotating and Cartesian coordinates. The waves are allowed to propagate at arbitrary angles to the uniform magnetic field, and no restrictions are imposed upon the mean Larmor radius, the frequencies, or the wave numbers. By electrostatic approximation of the dielectric tensor and the matrix elements the kinetic equations can be also applicable to the case in which the three waves are electrostatic altogether or partially electrostatic. The matrix elements in the limit of parallel or perpendicular propagation to the magnetic field are given.View full abstractDownload PDF (860K) -
Yutaka Nakai, Hisato Oyamatsu, Nobuhiko Kunitomi1989 Volume 58 Issue 8 Pages 2805-2809
Published: August 15, 1989
Released on J-STAGE: May 29, 2007
JOURNAL RESTRICTED ACCESSThe precession camera method of X-ray diffraction has revealed for β-Mn structure that 10 strong reciprocal-lattice points of {221} and {310}, form a slightly deformed decagon on the (1, 2.3, 5) plane. The symmetry and the local structure of the β-Mn structure are discussed in relation to the icosahedral symmetry.View full abstractDownload PDF (432K) -
Kiyosi Motida, Mizuhiko Ichikawa1989 Volume 58 Issue 8 Pages 2810-2816
Published: August 15, 1989
Released on J-STAGE: June 01, 2007
JOURNAL RESTRICTED ACCESSThe energy difference between the “up-down” and “lateral” H2PO4 configurations in the Slater model is interpreted as a difference in the molecular energies when they are fictitiously isolated while maintaining their configurations in the crystal. This version of the Slater model is shown to be satisfactory for explaining the observed correlation between the transition temperature and the covalent OH(D) bond length of the hydrogen bond OH(D)…O with a reasonable quantitative agreement. It is pointed out that the present model is not applicable to cases where the transition temperatures are very low.View full abstractDownload PDF (888K) -
Kêitsiro Aizu1989 Volume 58 Issue 8 Pages 2817-2825
Published: August 15, 1989
Released on J-STAGE: June 01, 2007
JOURNAL RESTRICTED ACCESSThe order parameters are assumed to number two, and denoted by Q and Q*. The free energy function is denoted by Φ. Let the degree of anisotropy of Φ in its gradient-less part be 2α, where α is an integer ≥2. The Lifshitz term, i.e., Q*∂zQ−Q∂zQ* and a term expressed as a product of Qα+Q*α or Qα−Q*α with Q*∂zQ−Q∂zQ* are interrelated as follows: If one of them is allowed (or forbidden) to exist in Φ, the other is always forbidden (or often allowed). Even if the former term is forbidden and no purely incommensurate phase is possible, a semicommensurate phase is possible owing to the latter term. (The coefficient to term ∂zQ∂zQ* is assumed to be positive.) On cooling, the prototypic phase can transform to the semicommensurate phase earlier than to the corresponding purely commensurate ferroic phase. A detailed explanation is given.View full abstractDownload PDF (1040K) -
Mikio Eto, Hiroshi Kamimura1989 Volume 58 Issue 8 Pages 2826-2835
Published: August 15, 1989
Released on J-STAGE: June 01, 2007
JOURNAL RESTRICTED ACCESSWe study the correlation effect on the electronic states in the uncompensated Si:P system from the intermediate to the critical concentration region, by the Multi-Configuration Self Consistent Field (MCSCF) method recently developed by the present authors. By simulating the Si:P system by a cluster model, we clarify the features of the Anderson-localized states and the nature of the metal-insulator transition from a new standpoint. It is shown that most of electrons form spin-singlet pairs and remaining pairs are spin-triplet. Near the metal-insulator transition, MCSCF one-electron orbitals near the Fermi level are extended and the correlation becomes weak by screening. This suggests the Mott-type transition.View full abstractDownload PDF (1188K) -
Masao Ogata, Hiroyuki Shiba1989 Volume 58 Issue 8 Pages 2836-2844
Published: August 15, 1989
Released on J-STAGE: June 01, 2007
JOURNAL RESTRICTED ACCESSIn strongly correlated systems the propagation of doped carriers always accompanies rearrangements of other particles so that it is inevitably an involved many-body problem. In this paper the momentum of the lowest-energy doped carriers is studied by determining exactly the ground state of small clusters. A comparative investigation is made on one-band and two-band systems: one-band Hubbard model in one and two dimensions and two-dimensional CuO2 model. Implications of the results are discussed in connection with high-Tc cuprates.View full abstractDownload PDF (1008K) -
Hiroshi Matsukawa, Hidetoshi Fukuyama1989 Volume 58 Issue 8 Pages 2845-2866
Published: August 15, 1989
Released on J-STAGE: May 29, 2007
JOURNAL RESTRICTED ACCESSThe effective Hamiltonian for high-Tc Cu-based oxide superconductors is derived based on Cu:dx2−y2 and O:pσ orbitals in the Cu–O plane by taking into account the intra- and nearest-neighbor interatomic Coulomb interactions for both cases of hole and electron doping. For hole doping, where the stability of Cu++ is assumed, the effective Hamiltonian proves to have various interaction processes, some features of which are studied by considering a case with a single Cu spin and one hole in the oxygen band. The spatial extent of the singlet-bound state in this case has been examined to the linear order of the oxygen band width. For electron doping the effective Hamiltonian is much simpler and essentially the same as the t-J model. Based on these results we discuss the relevance of the t-J model to the high-Tc Cu oxides. The effects of Cu:d3z2−r2 orbitals and O:pz orbitals at the apex of the pyramid or octahedron are also examined.View full abstractDownload PDF (1960K) -
Toshio Hayakawa, Daisuke Shimada, Nobuo Tsuda1989 Volume 58 Issue 8 Pages 2867-2876
Published: August 15, 1989
Released on J-STAGE: June 01, 2007
JOURNAL RESTRICTED ACCESSResistivity, Seebeck coefficient, and the magnetic susceptibility were measured for the sintered pellets to see if a random distribution of Ti and V makes the oxide insulating. The oxide seems to be an insulator in the composition range 0.8<x<1.2. The magnetic susceptibility followed the Curie-Weiss law with different constants below and above about 500 K for x>1. It was a sum of the Pauli paramagnetic one of Ti3+ electrons and the Curie-Weiss one of V3+ electrons for x<1. A mechanism of the metal-insulator transition was discussed.View full abstractDownload PDF (984K) -
Wolfgang Staguhn, Koichi Nakao, Noboru Miura, Michael von Ortenberg, S ...1989 Volume 58 Issue 8 Pages 2877-2883
Published: August 15, 1989
Released on J-STAGE: June 01, 2007
JOURNAL RESTRICTED ACCESSThe magnetoresistance was measured on oriented thin film TlBaCaCuO samples in pulsed high magnetic fields up to 40 T, by a PSD method at frequencies of 200 kHz, for the two fundamental orientations of the film in the magnetic field. Tc was defined at the midpoint of the transition curve. We obtained −dBc2⁄⁄⁄dT=20 T/K and −dBc2⊥⁄dT=0.6 T/K, for the magnetic field parallel and perpendicular to the film plane, respectively, which give a large anisotropy of the upper critical field Bc2(T) of 33. The estimated coherence lengths are ξ⊥(0)=0.8 Å and ξ⁄⁄(0)=28 Å.View full abstractDownload PDF (884K) -
Jun Kondo1989 Volume 58 Issue 8 Pages 2884-2895
Published: August 15, 1989
Released on J-STAGE: June 01, 2007
JOURNAL RESTRICTED ACCESSBased on the ionic crystal model, we have calculated the Madelung energies of several Cu–O based compounds: Tl2Ba2(Ca, Y)n−1CunO2n+4, Bi2Sr2(Ca, Y)n−1CunO2n+4 and TlBa2(Ca, Y)n−1CunO2n+3. We have determined the carrier distribution which makes the sum of the Madelung energy and the ionic energies of a compound the smallest. Our main concern is what the carriers are (holes or electrons) and which sites they occupy. We have found several different types of carrier distribution. When a large fraction of the Ca is replaced by Y in the substances with n≥3, electrons will be doped in the CuO2 planes where the Cu ions are in square-planar coordination.View full abstractDownload PDF (1164K) -
Hiroyuki Oyanagi, Kunihiko Oka, Hiromi Unoki, Yoshikazu Nishihara, Kei ...1989 Volume 58 Issue 8 Pages 2896-2901
Published: August 15, 1989
Released on J-STAGE: May 29, 2007
JOURNAL RESTRICTED ACCESSPolarized Cu K X-ray absorption fine structure (XAFS) has been measured on a single crystal of undoped La2CuO4−y for the first time, using a fluorescence detection technique. The polarized near-edge structure and EXAFS were strongly anisotropic, demonstrating the quasi-two-dimensional nature of electron states and local structure. The polarization dependence of the near-edge structure confirms that the Cu atoms take 2+ valence or d9 configuration with a strong fourfold Cu–O1 bonds within the CuO2 plane and weak twofold Cu–O2 bonds along the c-axis, which is consistent with the anisotropic local structure suggested by the Fourier transform of polarized EXAFS and a crystal structure.View full abstractDownload PDF (668K) -
Takashi Tonegawa, Isao Harada1989 Volume 58 Issue 8 Pages 2902-2915
Published: August 15, 1989
Released on J-STAGE: June 01, 2007
JOURNAL RESTRICTED ACCESSWe study the ground-state and finite-temperature properties of the one-dimensional isotropic spin-1/2 Heisenberg magnet with ferromagnetic nearest-neighbor and antiferromagnetic next-nearest-neighbor interactions which compete with each other. Extrapolating the exact results for finite-size systems of up to 20 spins, we estimate the ground-state energy and the ground-state two-spin correlation function in the infinite-size limit. Using the cluster transfer matrix method, we also calculate the temperature dependence of the internal energy and the specific heat and that of the inverse correlation length and the wave number, by both of which the asymptotic behavior of the two-spin correlation function in the long-distance limit is characterized. We compare the results of these calculations with those obtained previously for the case where the nearest-neighbor interaction is antiferromagnetic.View full abstractDownload PDF (1476K) -
Ko Mibu, Nobuyoshi Hosoito, Teruya Shinjo1989 Volume 58 Issue 8 Pages 2916-2924
Published: August 15, 1989
Released on J-STAGE: May 29, 2007
JOURNAL RESTRICTED ACCESSMultilayered films with artificial superstructures were prepared by alternate deposition of Fe and Nd in ultrahigh vacuum. Individual layer thicknesses of Fe and Nd layer were varied from 7 Å to 52 Å and 3 Å to 46 Å, respectively. From 57Fe Mössbauer measurements, the direction of Fe magnetic moments for the samples [Fe(26∼39 Å)/Nd(7∼14 Å)] is found to be nearly perpendicular to the film plane both at 300 K and 4.2 K. In contrast, for the samples [Fe(26∼52 Å)/Nd(28∼46 Å)], the direction at 300 K is in-plane but changes to the perpendicular direction at low temperature. The relationship between the perpendicular magnetic anisotropy and the magnetization of interface Nd atoms is discussed.View full abstractDownload PDF (916K) -
Yoshikazu Nishihara, Haruhiko Obara, Toshikazu Katayama, Hiroyuki Oyan ...1989 Volume 58 Issue 8 Pages 2925-2929
Published: August 15, 1989
Released on J-STAGE: May 29, 2007
JOURNAL RESTRICTED ACCESSMössbauer spectra of 57Fe in YBa2(Cu1−xFex)3Oy were studied for the samples keeping the oxygen concentration constant, y=6.87±0.05. Using the results of EXAFS measurement, we find that changes in the Mössbauer pattern with iron concentration can be explained from changes in the oxygen coordination around iron. The number of iron atoms with an octahedral coordination increases rapidly with a change in the crystal structure from orthorhombic to tetragonal. This increase has a close correlation with the decrease in a zero-field cooled magnetization in the superconducting state. These results are consistent with that the tetragonal structure observed by X-ray diffraction is induced by the increase of the number of octahedrally coordinated iron and consists of microdomains with the orthorhombic structure inside the domains.View full abstractDownload PDF (612K) -
Hidekazu Tanaka, Yusto Kaahwa, Toshiaki Hasegawa, Masukazu Igarashi, S ...1989 Volume 58 Issue 8 Pages 2930-2951
Published: August 15, 1989
Released on J-STAGE: June 01, 2007
JOURNAL RESTRICTED ACCESSWe report the results of ESR and magnetic measurements on single crystals of KNiCl3 whose chemical unit cell at room temperature is described by enlarging that of CsNiCl3 to \sqrt3a, \sqrt3a, c, containing three –NiCl3– chains (two on the A-site and one on the B-site). The intrachain exchange interaction constant was estimated to be J0⁄kB=−15 K. The magnetic anisotropy was found to be the easy-plane type and D⁄kB=−0.86 K. Three-dimensional ordering occurs at TN=8.2 K. In the ordered state an ESR mode which is unexplainable in terms of the usual two-sublattice model was observed. Introducing two kinds of interchain exchange interactions, J1AB and J1AA, and taking six sublattices, we investigate the normal modes for the motions of the sublattice magnetizations. The frequency-field diagram calculated with J1AB⁄kB=−1.3×10−2 K and J1AA⁄kB=−1.1×10−2 K is in good agreement with the experimental one.View full abstractDownload PDF (2028K) -
Takashi Fujikawa, Toshinaga Okazawa, Kazuo Yamasaki, Jing-Chang Tang, ...1989 Volume 58 Issue 8 Pages 2952-2961
Published: August 15, 1989
Released on J-STAGE: June 01, 2007
JOURNAL RESTRICTED ACCESSIn this work we studied the Na K-edge XANES spectra of pure NaCl crystal and NaCl–KCl mixed crystal measured by Murata et al. to clarify the geometric and electronic structure around X-ray absorbing atoms by use of the short-range order full multiple scattering calculation. The changes observed in the experimental XANES for the increase of KCl concentration are qualitatively explained by assuming that in a very small scale NaCl and KCl grains are to be in contact with each other. We also found that the Na–Cl distance in the boundary region remains nearly the same as in NaCl crystal. The net charge on Na ion in pure NaCl crystal is also estimated and found to be slightly smaller than that in NaF crystal.View full abstractDownload PDF (1100K) -
Kazuo Yamasaki, Takashi Fujikawa, Shun-ichi Nakai1989 Volume 58 Issue 8 Pages 2962-2967
Published: August 15, 1989
Released on J-STAGE: May 29, 2007
JOURNAL RESTRICTED ACCESSWe performed numerical calculations for fluorine K-edge XANES of MnF2 by use of our short-range-order full multiple scattering theory developed previously. From the comparison between the observed and calculated XANES, we estimated the net charge on the fluorine ion (−q) and d electron number (d); (q=0.3, d=4.8∼5.2. This result is consistent with those obtained by other theoretical and experimental methods.View full abstractDownload PDF (548K) -
L. F. Chen, C. H. Leung, K. S. Song1989 Volume 58 Issue 8 Pages 2968-2975
Published: August 15, 1989
Released on J-STAGE: May 29, 2007
JOURNAL RESTRICTED ACCESSThe electronic structure of various types (one-center, two-center, and dimer complex) of self-trapped excitons (STE’s) in alkali halide crystals containing heavy halogen impurity atoms, has been studied by the extended-ion method (developed earlier for STE’s in pure alkali halides) coupled with a CNDO code. Results of the calculations for KCl:I, RbCl:I, and KCl:Br are generally in satisfactory agreement with experiment. In particular, two distinct configurations have been found for the two-centre type STE’s, which accounts for the blue and the blue-green emission bands. A general discussion of defect (F–H pair) formation mechanism in these systems, consistent with experimental observations, has also been presented.View full abstractDownload PDF (996K) -
Mitsuhiro Furukawa, Ken-ichi Mizuno, Atsuo Matsui, S. D. D. V. Rughoop ...1989 Volume 58 Issue 8 Pages 2976-2987
Published: August 15, 1989
Released on J-STAGE: June 01, 2007
JOURNAL RESTRICTED ACCESSIntegrated luminescence spectra, time-resolved luminescence spectra, and luminescence decay times of stretch-oriented poly(phenylenevinylene) (PPV) are studied in the temperature range 300∼12 K. The reflectance spectrum at room temperature is also studied. The luminescence spectrum is composed of vibronic bands and a broad band, which are interpreted as caused by radiative annihilation of free and self-trapped excitons, respectively. Temperature dependence of the intensity of free-exciton luminescence and temperature dependence of the decay time are interpreted in terms of relaxation of excitons. The height of a potential barrier, which separates the free exciton state and the self-trapped state, is found to be 350 cm−1. At 20 K, exciton relaxation toward the self-trapped state occurs by a quantum-mechanical tunneling process. The tunneling rate obtained is (90 ps)−1.View full abstractDownload PDF (1516K) -
Hidenobu Hori, Noritaka Kuroda, Hiroshi Yamamoto, Yuichirô Nishi ...1989 Volume 58 Issue 8 Pages 2988-2993
Published: August 15, 1989
Released on J-STAGE: May 29, 2007
JOURNAL RESTRICTED ACCESSThe Zeeman effect of the R-lines in alexandrite was investigated by using pulsed high magnetic fields up to 400 kOe. Well separated Zeeman splitting of R-lines was observed below liquid nitrogen temperature. Different from the R-lines in ruby, all the transitions with ΔSz=0, ±1 and ±2 are observed in alexandrite reflecting the lower symmetry on the Cr3+ ion site. The excited state g-values along the a-, b- and c-axes are experimentally determined as 1.6, 1.4 and 1.3 for the A′-state (R1) and 2.0, 1.4 and 1.4 are obtained for the A″-state (R2), respectively.View full abstractDownload PDF (604K)