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Volume 74, Issue 5
Displaying 1-50 of 54 articles from this issue
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Katsuya Shimizu, Kiichi Amaya, Naoshi Suzuki2005 Volume 74 Issue 5 Pages 1345-1357
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSBoth experimental and theoretical approaches in our search for superconductivity under pressure are reviewed. We have developed a double extreme condition of very low-temperature down to 50 mK using a 3He/4He dilution refrigerator and ultrahigh pressure up to 200 GPa using a diamond-anvil cell (DAC). Experimental techniques producing ultrahigh pressure as well as measuring electrical resistance, magnetization and optical response are developed especially for studying the pressure-induced superconductivity of simple systems such as elemental materials. The details of these techniques are described in §1. In §2, we review several examples of pressure-induced superconductivity observed for the first time by our group. Comparisons between experimental results and theories based on the first principles band calculations are given in §3. Finally, we point out remaining problems to be solved in further studies in the search for pressure-induced superconductivity.View full abstractDownload PDF (407K) -
Lizhu Tong, Kenichi Nanbu2005 Volume 74 Issue 5 Pages 1359-1361
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSUsing the measured swarm parameters of SF6−, SF5−, and F− ions in SF6 gas, an ion-molecule collision model based on Nanbu and Kitatani’s theory [J. Phys. D 28 (1995) 324] is constructed. The model works well for a wide range of reduced electric field E⁄N of 5–1000 Td (1Td=10−21 V m2). The model is usable for the particle modeling of SF6 discharge.View full abstractDownload PDF (122K) -
Akio Nakahara, Yousuke Matsuo2005 Volume 74 Issue 5 Pages 1362-1365
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSIn the drying process of a paste, we can imprint a memory into the paste that determines how it will be broken in the future. That is, if we vibrate the paste before it is dried, it remembers the direction of the initial external vibration, and the morphology of the resultant crack patterns is determined solely by the memory of this direction. The morphological phase diagram of crack patterns and the rheological measurement of the paste show that this memory effect is induced by the plasticity of the paste.View full abstractDownload PDF (105K) -
Takeshi Akinaga, Jiro Mizushima2005 Volume 74 Issue 5 Pages 1366-1369
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSThe linear stability of flow past two circular cylinders in a side-by-side arrangement is investigated theoretically, numerically and experimentally under the assumption of a two-dimensional flow field, in order to explore the origin of in-phase and antiphase oscillatory flows. Steady symmetric flow is realized at a small Reynolds number, but becomes unstable above a critical Reynolds number though the solution corresponding to the flow still satisfies the basic equations irrespective of the magnitude of the Reynolds number. We obtained the solution numerically and investigated its linear stability. We found that there are two kinds of unstable modes, i.e., antisymmetric and symmetric modes, which lead to in-phase and antiphase oscillatory flows, respectively. We determined the critical Reynolds numbers for the two modes and evaluated the critical distance at which the most unstable disturbance changes from the antisymmetric to the symmetric mode, or vice versa.View full abstractDownload PDF (499K) -
Hiromi Taniguchi, Masashi Miyashita, Kenichi Uchiyama, Ryosuke Sato, Y ...2005 Volume 74 Issue 5 Pages 1370-1373
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSWe have investigated the resistivity of an organic Mott insulator, β′-(BEDT-TTF)2AuCl2, under extremely high pressures of up to 9.9 GPa, using the cubic anvil press, motivated by the fact that a related material, β′-(BEDT-TTF)2ICl2, shows the highest transition-temperature superconductivity among organics at 8.2 GPa. Through characterization by resistivity and susceptibility measurements at ambient pressure, we have confirmed that these two salts have common physical properties. Nevertheless, β′-(BEDT-TTF)2AuCl2 does not show superconductivity but remains semiconducting up to 9.9 GPa. We discuss the origin of these contrasting behaviors and suggest the cause to be the difference in anion size between the two salts.View full abstractDownload PDF (2531K) -
Yasuhiro Hatsugai2005 Volume 74 Issue 5 Pages 1374-1377
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSWe propose the use of generic Chern numbers for the characterization of topological insulators. It is suitable for the numerical characterization of low-dimensional quantum liquids, in which strong quantum fluctuations prevent the development of conventional orders. Using the twisting parameters of boundary conditions, the non-Abelian Chern numbers are defined for a few low-lying states near the ground state in a finite system, which is a ground state multiplet with a possible (topological) degeneracy. We define the system as a topological insulator when energies of the multiplet are well separated from the above. Translational invariant twists up to a unitary equivalence are crucial to picking up only bulk properties without edge states. As a simple example, the setup is applied to a two-dimensional XXZ-spin system with an Ising anisotropy, in which the ground state multiplet is composed of doubly almost degenerate states. It gives a vanishing Chern number due to symmetry. Also Chern numbers for the generic fractional quantum Hall states are discussed briefly.View full abstractDownload PDF (165K) -
Takao Nakama, Yoshinao Takaesu, Katsuma Yagasaki, Takashi Naka, Akiyuk ...2005 Volume 74 Issue 5 Pages 1378-1381
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSThe electrical resistivity ρ and thermopower S of Heusler compounds Fe3−xVxAl have been measured at the temperature range from 1.5 to 300 K at magnetic fields up to 15 T. The measurements of ρ and S in the high temperature range up to 800 K have been performed. ρ and S show a semiconducting behavior at high temperatures, and the obtained experimental energy gap increases almost linearly with increasing V concentration x. S is positive for x<1.0 and negative for x≥1.0 at all measured temperatures, indicating a drastic change of major carriers at x=1.0. The electron scattering due to the magnetic fluctuations of Fe clusters has a dominant effect on the behavior of ρ of the magnetic compounds at low temperatures. On the other hand, S is not sensitive to the magnetic state and the external magnetic field, which is related to the energy dependence of magnetic scattering at the Fermi level.View full abstractDownload PDF (222K) -
Eiichi Matsuoka, Katsuyuki Hayashi, Akiko Ikeda, Kazue Tanaka, Toshiro ...2005 Volume 74 Issue 5 Pages 1382-1385
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSThe magnetic, transport and thermal properties of alkaline-earth-filled skutterudites AFe4Sb12 (A = Ca, Sr, Ba) are reported. All three compounds show maximum magnetic susceptibility and thermopower at 50 K and a large electronic specific heat coefficient of 100 mJ/mol K2. The electrical resistivity exhibits a shoulder at 70 K and follows quadratic temperature dependence below 9 K. These properties are the characteristics of a nearly ferromagnetic metal. The suppression of ferromagnetic spin fluctuations of the Fe 3d band by applying magnetic fields was manifested as a negative magnetoresistance between 50 and 80 K.View full abstractDownload PDF (161K) -
Hiroyuki Takagiwa, Sogo Kuroiwa, Maki Yamazawa, Jun Akimitsu, Kazuki O ...2005 Volume 74 Issue 5 Pages 1386-1389
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSWe report on the magnetic penetration depth, λ, in a type II superconductor NbB2+x determined by muon spin rotation/relaxation measurements. We show in the sample with x=0.1 that λ at 2.0 K is independent of an applied magnetic field. This suggests that the superconducting order parameter in NbB2+x is isotropic, as expected for conventional BCS superconductors. Meanwhile, the superconducting carrier density (∝λ−2) exhibits an interesting tendency of increase with increasing Tc (where Tc varies with x), which is described by the weak-coupling BCS theory.View full abstractDownload PDF (194K) -
Takashi Koretsune, Masao Ogata2005 Volume 74 Issue 5 Pages 1390-1393
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSThe equal-time pairing correlation function of the two-dimensional t–J model on a square lattice is studied using a high-temperature expansion method. The sum of the pairing correlation, its spatial dependence, and the correlation length are obtained as functions of temperature down to T\\simeq0.2t. By comparison of single-particle contributions in the correlation functions, we find an effective attractive interaction between quasi-particles in dx2−y2-wave pairings. It is shown that d-wave correlation grows rapidly at low temperatures for 0.5<n<0.9, with n being the electron density. The temperature for this growth is roughly scaled by J⁄2. This is in sharp contrast to the Hubbard model in a weak or intermediate coupling region, where there is no numerical evidence of superconductivity.View full abstractDownload PDF (114K) -
Jun Goryo, Hiroshi Matsukawa2005 Volume 74 Issue 5 Pages 1394-1396
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSWe investigate the flux flow state in a two-gap superconductor in which two s-wave gaps with different amplitudes exist on two separate Fermi surfaces. The flux flow resistivity is obtained on the basis of the Bardeen–Stephen relation and the result agrees well with the anomalous field dependence of the flow resistivity recently observed in the two-gap superconductor MgB2. Some typical properties of the vortex in this system are also discussed.View full abstractDownload PDF (115K) -
Sotaro Sasaki, Hiroaki Ikeda, Kosaku Yamada2005 Volume 74 Issue 5 Pages 1397-1400
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSWe investigate the mass enhancement factor and the superconducting transition temperature in the d–p model for the high-Tc cuprates. We solve the Éliashberg equation using the third-order perturbation theory with respect to the on-site Coulomb repulsion U. We find that when the energy difference between the d-level and p-level is large, the mass enhancement factor becomes large and Tc tends to be suppressed owing to the difference of the density of state for d-electron at the Fermi level. From another viewpoint, when the energy difference is large, the d-hole number approaches unity and the electron correlation becomes strong and enhances the effective mass. This behavior for the electron number is the same as that for the f-electron number in the heavy fermion systems. The mass enhancement factor plays an essential role in understanding the difference in Tc between the LSCO and YBCO systems.View full abstractDownload PDF (118K) -
Hiroaki Matsui, Daisuke Hashimoto, Seigo Souma, Takafumi Sato, Takashi ...2005 Volume 74 Issue 5 Pages 1401-1403
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSWe have performed ultrahigh-resolution photoemission spectroscopy on the intermetallic superconductor hexagonal h-ZrRuP (Tc=13 K). We observed the opening of a superconducting gap below Tc, and found that the most probable order parameter is s-wave with a gap size (Δ) of 1.8 meV at 6 K. This gap size gives 2Δ0⁄kBTc∼3.5, suggesting the weak-coupling nature of the superconductivity in h-ZrRuP. We also observed a pseudogap-like suppression of spectral weight up to ∼45 meV from the Fermi level, indicative of the strong coupling of electrons with phonons and/or the charge density wave fluctuation.View full abstractDownload PDF (99K) -
R. B. Chen, C. P. Chang, J. S. Hwang, D. S. Chuu, M. F. Lin2005 Volume 74 Issue 5 Pages 1404-1407
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSMagnetoelectronic properties of finite carbon nanotubes (CNs) are studied for an arbitrary field direction. They are strongly affected by the nanotube geometry (length, radius; boundary structure), the magnitude and direction of the magnetic field, the Zeeman effect, and the temperature. Geometric structures determine electronic structures and magnetic properties, which thus leads to three types of energy gaps and induced magnetic fields. The critical angle, which corresponds to the change of magnetism, exists in armchair CNs, but not in zigzag CNs. It also depends on the length and the radius of CNs. Finite CNs are very different from infinite CNs. Zeeman splitting could induce complete energy-gap modulation, a drastic change in magnetization, and a gigantic paramagnetic response for all zigzag CNs. The predicted results are observable even at room temperature.View full abstractDownload PDF (302K) -
Jan Kuneš, Wei Ku, Warren E. Pickett2005 Volume 74 Issue 5 Pages 1408-1411
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSUsing a density functional method with explicit account for strong Coulomb repulsion within the 4f shell, we calculate effective exchange parameters and the corresponding ordering temperatures of the (ferro)magnetic insulating Eu monochalcogenides (EuX; X = O, S, Se, Te) at ambient and elevated pressure conditions. Our results provide quantitative account of the many-fold increase of the Curie temperatures with applied pressure and reproduce well the decrease of ferromagnetic coupling across the EuO–EuTe series. The first J1 and second J2 neighbor effective exchange are found to follow different pressure dependencies. Finally, our calculations show explicitly that the mixing of Eu 4f orbitals with the ligand states is necessary for the ferromagnetic ordering to take place at any pressure.View full abstractDownload PDF (362K) -
Masaaki Matsuda, Akiko Kikkawa, Koichi Katsumata, Shuji Ebisu, Shoichi ...2005 Volume 74 Issue 5 Pages 1412-1415
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSNeutron diffraction measurements on a powder sample of α-160Gd2S3 are performed. This material consists of a stacking of square lattice Gd1 and triangular Gd2 planes and exhibits a novel phase transition that was interpreted as being due to geometrical frustration. The magnetic unit cell is found to be the same as the chemical unit cell. The magnetic moments order parallel with each other along the b-axis. The magnetic structure in the ac plane is such that a Gd1 moment is ordered antiparallel to the nearest neighboring Gd1 moments and is coupled parallel to the next-nearest neighboring Gd1 moments. The Gd2 moment is coupled antiparallel to the nearest neighboring Gd1 moment. The temperature dependence of the order parameter is extracted and is found to be explained rather well by the result of an S=7⁄2 molecular field approximation. The collinear structure of the magnetic moments in the triangular lattice and the absence of large magnetic fluctuations around the magnetic transition temperature suggest that the geometrical frustration is not so distinct in α-Gd2S3.View full abstractDownload PDF (275K) -
Masaki Maeda, Koji Okada, Kiyoshi Deguchi, Makoto Iwata, Ikuo Suzuki2005 Volume 74 Issue 5 Pages 1416-1418
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSDielectric dispersion studies have been performed on pyridinium tetrafluoroborate single crystals in the frequency range of 300 Hz to 20 MHz. The measurements have been carried out in the temperature range from 190 to 300 K. In the vicinity of the paraelectric-to-ferroelectric phase transition temperature (T1), the process of dielectric critical slowing down was observed. Two Debye-type relaxational modes were observed below the phase transition temperature (T1). The observed dielectric dispersion in the vicinity of T1 was analyzed using a model with a single Debye-type relaxation mode, and the dispersion below T1 was analyzed using a model with two Debye-type relaxation modes.View full abstractDownload PDF (91K) -
Taka-hisa Arima, Jong-Hoon Jung, Masakazu Matsubara, Masato Kubota, Ji ...2005 Volume 74 Issue 5 Pages 1419-1422
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSWe report on the first observation of magnetoelectric X-ray scattering (MEXS), i.e., incident-k-direction-dependent scattering, for a polar ferrimagnet GaFeO3. Near the K edge of Fe, the magnetic component of the (040) X-ray reflection shows a larger enhancement than that of the (020) X-ray reflection, which cannot be attributed to the genuine magnetic scattering, but to the MEXS of Fe3+ ions. Toroidal moments as defined by the outer product of the Fe off-center displacement and the magnetic moment show ferroic ordering, which causes the resonant MEXS at the Fe 1s–3d excitation energy.View full abstractDownload PDF (146K) -
Takeshi Tayagaki, Andre Mysyrowicz, Makoto Kuwata-Gonokami2005 Volume 74 Issue 5 Pages 1423-1426
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSWe report on the observation of the yellow exciton Lyman series up to the fourth term in Cu2O by time-resolved mid-infrared spectroscopy. The dependence of oscillator strength on the principal quantum number n can be well reproduced using the hydrogenic model including an AC dielectric constant, and precise information on the electronic structure of the 1s exciton state can be obtained. A Bohr radius a1s=7.9 Å and a 1s–2p transition dipole moment μ1s–2p=4.2 eÅ were found.View full abstractDownload PDF (115K) -
Kimiaki Konno, Hiroshi Kakuhata2005 Volume 74 Issue 5 Pages 1427-1430
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSA hierarchy for integrable equations of stretched vortex filament is derived with the inverse scattering method in which a natural extension of the local induction equation is obtained. An infinite number of conserved quantities is presented.View full abstractDownload PDF (70K) -
Exact Solutions with Jacobi Elliptic Functions of Two Nonlinear Models for Ion-Acoustic Plasma WavesA. H. Khater, M. M. Hassan, R. S. Temsah2005 Volume 74 Issue 5 Pages 1431-1435
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSThe periodic wave solutions of two nonlinear models for ion-acoustic plasma waves, including the mixed Korteweg–de Vries (KdV) and modified KdV equation and the (3+1)-dimensional modified Zakharov–Kuznetsov equation, are obtained by using the F-expansion method and introducing appropriate transformations. In the limiting cases, the solitary wave solutions of the equations are also obtained.View full abstractDownload PDF (88K) -
Sachiko Kitajima, Masashi Ban, Fumiaki Shibata2005 Volume 74 Issue 5 Pages 1436-1444
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSDynamics of quantum information channel is studied with the use of a boson detector model. Explicit results are given for quantum dense coding process on the basis of an equivalence relation between a classical capacity and von Neumann mutual information. Reduced density matrices for an entangled spin degree of freedom of an incoming particle are exactly solved to give complete time evolution under influence of fluctuations due to a detector. Quantum mechanical channel matrix and the classical capacity are determined as functions of time and temperature. Decoherence properties of the entangled states under quantum and thermal noises are fully discussed.View full abstractDownload PDF (152K) -
Sang Wook Kim, Hwa-Kyun Park2005 Volume 74 Issue 5 Pages 1445-1448
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSUsually, decoherence is generated from the coupling with an outer environment. However, a macroscopic object generically possesses its own environment in itself, namely the complicated dynamics of internal degrees of freedom. We address a question: when and how the internal dynamics decohere interference of the center of mass motion of a macroscopic object. We will show that weak localization of a macroscopic object in disordered potentials can be destroyed by such decoherence.View full abstractDownload PDF (85K) -
C. C. Mak, K. W. Chow, K. Nakkeeran2005 Volume 74 Issue 5 Pages 1449-1456
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSThe dynamics of nonlinear pulse propagation in an averaged dispersion-managed soliton system is governed by a variable coefficient nonlinear Schrödinger equation (NLSE). For a special set of parameters the variable coefficient NLSE is completely integrable. The same variable coefficient NLSE is also applicable to optical fiber systems with phase modulation or pulse compression. For such variable coefficient NLSE, solitary waves have been computed earlier in the literature either by the inverse scattering transform or the Bäcklund transformation. The Hirota bilinear method is shown to be applicable here too, and this modified format is employed to compute the exact bright and dark soliton solutions and the periodic waves solutions. The analysis is also extended to the coupled variable coefficient NLSEs. The merit of the Hirota bilinear approach is demonstrated clearly as periodic and solitary waves are obtained even for nonintegrable coupled systems. The validity of the new solutions is verified directly and independently by the software Mathematica.View full abstractDownload PDF (2894K) -
Kenichi Kanai, Akiko Ugawa, Osamu Sano2005 Volume 74 Issue 5 Pages 1457-1463
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSAn experimental study was made to elucidate the effect of three dimensionality of particle dynamics as well as the number of layers necessary for the pattern formation in vibrating granular layer. We observed “ripple” and “undulation” of various modes in a container whose separation distance of the vertical walls was as small as one particle diameter size, and obtained the critical number of layers about three for the formation of these patterns. Particle trajectories were traced, which revealed eight-figured motion of particles in ripple patterns. On the other hand, configuration change of densely packed particles at the time of impingement on the bottom of the container was found to be characteristic of undulation patterns.View full abstractDownload PDF (428K) -
Takashi Ishihara, Yukio Kaneda, Mitsuo Yokokawa, Ken’ichi Itakur ...2005 Volume 74 Issue 5 Pages 1464-1471
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSThe energy spectrum in the near dissipation range of turbulence is studied by analyzing the data of a series of high-resolution direct numerical simulations of incompressible homogeneous turbulence in a periodic box with the Taylor micro-scale Reynolds number Rλ and resolution ranging up to about 675 and 40963, respectively. The spectra in the Reynolds number range fit well to the form C(kη)αexp(−βkη) in the wavenumber range 0.5\\lesssimkη\\lesssim1.5, where η is the Kolmogorov dissipation length scale and C, α and β are constants independent of k. The values of α and β decrease monotonically with Rλ, and they are consistent with the conjecture that they approach to constants as Rλ→∞, but the approach, especially that of β, is slow.View full abstractDownload PDF (268K) -
Sung-Ik Sohn, Woonjae Hwang2005 Volume 74 Issue 5 Pages 1472-1478
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSThe nonlinear evolution of an interface subject to a parallel shear flow is studied on the basis of the vortex sheet model. We perform numerical simulations of the vortex sheet in density stratified fluids by using the point vortex method. The numerical algorithm based on two types of regularization method improves the stability of the vortex method and provides solutions with much higher resolutions than previous results. The numerical results show that, for a smaller density ratio, the interface has a larger growth rate and a more singular vortex sheet strength and curvature at late times. It is also found that, for an infinite density ratio, the interface has a solution of a travelling wave with no deformations.View full abstractDownload PDF (348K) -
Yoshinori Mizuno, Mitsuaki Funakoshi2005 Volume 74 Issue 5 Pages 1479-1489
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSThe dependence of the chaotic mixing of fluids on the Reynolds number Re in a partitioned-pipe mixer (PPM), composed of alternately placed horizontal and vertical plates in a rotating cylinder, is studied. By numerically calculating the steady velocity field due to this rotation and an axial pressure gradient, we find that the three-dimensionality of the velocity field becomes weaker with increasing Re from zero. From the computation of trajectories of fluid particles in this velocity field, we also find that tubular transport barriers extending straight in the axial direction initially expand as Re is increased. Although these barriers usually disappear with the further increase in Re, some of them survive even up to a relatively large Re when the ratio of the lengths of neighboring plates is markedly different from unity. Moreover, high-shear regions are observed away from the rigid walls for a sufficiently large Re. Therefore, we conclude that the size of the transport barriers does not simply depend on Re, and that the mixing efficiency outside these barriers is expected to be enhanced by the appearance of high-shear regions with increasing Re.View full abstractDownload PDF (1775K) -
Akira Sakurai, Shuji Takahashi2005 Volume 74 Issue 5 Pages 1490-1495
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSThis paper addresses the analytical solution of the flow field of a single weak Mach reflection caused by an advancing plane shock wave over a simple wedge surface. We develop an improvement of Lighthill’s linearized theory in the correction due to the non-linearity of the flow field through a singular perturbation. Obtained results are utilized to demonstrate the relation between incident and reflected shock wave angles for the resolution of the von Neumann paradox.View full abstractDownload PDF (185K) -
Woong Lee, Yo-Han Yoo, Hyunho Shin, Jae-Min Myoung2005 Volume 74 Issue 5 Pages 1496-1499
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSRole of the composition of InxGa1−xAs strain-relief layer (SRL) in controlling the strain fields and consequent modification of band structures in a close-stacked multi-layer InAs/GaAs quantum dot (QD) system was investigated within the framework of continuum elasticity and model solid theory. It was predicted that strains in the QDs are significantly relieved in proportion to the In concentration in the InxGa1−xAs SRLs between InAs QD and GaAs cap layer. The relaxation of strains caused substantial shift of the conduction band edge in the QDs mainly by the relief of hydrostatic strain component resulting in narrower bandgap within the QDs with increasing In concentration. It is interpreted that such strain relaxation and subsequent band structure modifications are responsible for the experimentally observed redshift of photo-luminescence (PL) spectra elsewhere. Therefore, together with existing experimental work, it is confirmed that conduction band edges of QD systems can be tailored by the control of the SRL composition allowing more flexibility in bandgap engineering.View full abstractDownload PDF (145K) -
Takeshi Matsumura, Daisuke Okuyama, Nobuyuki Oumi, Kazuma Hirota, Hiro ...2005 Volume 74 Issue 5 Pages 1500-1507
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSResonant x-ray scattering (RXS) experiment has been performed for the (3 0 1.5) superlattice reflection in the antiferroquadrupolar and antiferromagnetic phase of DyB2C2. Azimuthal-angle dependence of the resonance enhanced intensities for both dipolar (E1) and quadrupolar (E2) resonant processes has been measured precisely with polarization analysis. Every scattering channel exhibits distinctive azimuthal dependence, differently from the symmetric reflection at (0 0 0.5) which was studied previously. We have analyzed the results using a theory developed by Lovesey et al. [J. Phys.: Condens. Matter 8 (1996) 10983], which directly connects atomic tensors with the cross-section of RXS. The fitting results indicate that the azimuthal dependences can be explained well by the atomic tensors up to rank 2. Rank 4 tensor is not reflected in the RXS data. In addition, the coupling scheme among the 4f quadrupolar moment, 5d ortital, and the lattice has been determined from the interference among the Thomson scattering from the lattice distortion and the resonant scatterings of E1 and E2 processes. It has also been established from the RXS of the (3 0 1.5) reflection that the canting of the 4f quadrupolar moments exists up to TQ. We also discuss a possible wavefunction of the ground state and the existence of the rank 4 moment.View full abstractDownload PDF (427K) -
K. Okabe, J.-I. Yamaura, A. Miyazaki, T. Enoki2005 Volume 74 Issue 5 Pages 1508-1520
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSThe crystal structure and electronic and magnetic properties of magnetic molecular conductor (EDTDM)2FeBr4 are investigated. The material undergoes a SDW transition at TMI∼11 K and an antiferromagnetic transition of Fe3+ d-spins at TN=3 K. In addition to the appearance of an anomaly in the resistivity around TN, a large magnetoresistance is observed below TN, which diverges at the critical pressure (Pc∼9.2 kbar) of the MI transition. The perturbation potential from the antiferromagnetic Fe3+ spin arrangement stabilizes the SDW state, leading to the anomaly in the resistivity. The application of magnetic field reduces the potential of the Fe3+ spins, which leads to the large negative magnetoresistance. This indicates that the π–d interaction plays an important role in the interplay between the magnetism and the electron transport.View full abstractDownload PDF (827K) -
Hiroshi Sakai, Yositake Takane2005 Volume 74 Issue 5 Pages 1521-1524
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSThe conductance of disordered wires with symplectic symmetry is studied by a random-matrix approach. It has been shown that the behavior of the conductance in the long-wire limit crucially depends on whether the number of conducting channels is even or odd. We focus on the metallic regime where the wire length is much shorter than the localization length, and calculate the ensemble-averaged conductance and its variance for both the even- and odd-channel cases. We find that the weak-antilocalization correction to the conductance in the odd-channel case is equivalent to that in the even-channel case. Furthermore, we find that the variance dose not depend on whether the number of channels is even or odd. These results indicate that in contrast to the long-wire limit, clear even–odd differences cannot be observed in the metallic regime.View full abstractDownload PDF (80K) -
Satoshi Okada, Ichiro Terasaki, Hirotaka Okabe, Masanori Matoba2005 Volume 74 Issue 5 Pages 1525-1528
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSResistivity, thermopower and Hall coefficient have been systematically measured for polycrystalline samples of (Bi1−xPbx)1.8Ba2Rh1.9Oy. An upturn of the resistivity and the Hall coefficient below 50 K is ascribed to decrease in the density of states due to a pseudogap formation. The thermopower and Hall coefficient are nearly identical to those of the thermoelectric oxide Bi2Sr2Co2Oy. This suggests a nearly identical density of states between the two oxides, which is also verified from a first-principle calculation, where a broader 4d orbital and a larger rhodium-rhodium distance along the in-plane direction accidentally give nearly the same density of states as those of the layered cobalt oxides.View full abstractDownload PDF (125K) -
Tadashi Kawamoto, Takehiko Mori, Taichi Terashima, Shinya Uji, Ayumi T ...2005 Volume 74 Issue 5 Pages 1529-1533
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSSuperconducting properties are investigated for the incommensurate ambient pressure organic superconductor (MDT-ST)(I3)0.417 [MDT-ST: 5H-2-(1,3-dithiol-2-ylidene)-1,3-diselena-4,6-dithiapentalene, Tc=4.3 K]. The upper critical fields show anisotropic three-dimensional angle dependence in contrast to the highly two-dimensional one. Although the coherence lengths are highly anisotropic ξ||c:ξ||b:ξ||a∼1:8:11, the interlayer coherence length, ξ||c, is much longer than the thickness of the conducting sheet. These results indicate that the present compound is a highly anisotropic three-dimensional superconductor among the layered organic superconductors. The superconducting transition widths in the conducting plane exhibit anomalous decreases with decreasing temperature, suggesting that the flux-lines are pinned by infinite anion chains.View full abstractDownload PDF (544K) -
Youichi Yanase, Masao Ogata2005 Volume 74 Issue 5 Pages 1534-1543
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSThe mechanism of high-Tc superconductivity is investigated with interests on the microscopic aspects of the condensation energy. The theoretical analysis is performed on the basis of the FLEX approximation which is a microscopic description of the spin-fluctuation-induced-superconductivity. Most of phase transitions in strongly correlated electron system arise from the correlation energy which is copmetitive to the kinetic energy. However, we show that the kinetic energy cooperatively induces the superconductivity in the underdoped region. This unusual decrease of kinetic energy below Tc is induced by the feedback effect which alters the properties of quasi-particles, such as mass renormalization and lifetime. The crossover from BCS behavior to this unusual behavior occurs for hole dopings. On the other hand, the decrease of kinetic energy below Tc does not occur in the electron-doped region. We discuss the relation to the recent obserbation of the violation of optical sum rule.View full abstractDownload PDF (196K) -
Takahiro Murashima, Keigo Hijii, Kiyohide Nomura, Takashi Tonegawa2005 Volume 74 Issue 5 Pages 1544-1551
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSThe one dimensional S=1 XXZ model with next-nearest-neighbor interaction α and Ising-type anisotropy Δ is studied by using a numerical diagonalization technique. We discuss the ground state phase diagram of this model numerically by the twisted-boundary-condition level spectroscopy method and the phenomenological renormalization group method, and analytically by the spin wave theory. We determine the phase boundaries among the XY phase, the Haldane phase, the ferromagnetic phase and the Néel phase, and then we confirm the universality class. Moreover, we map this model onto the non-linear σ model and analyze the phase diagram in the α<<−1 and Δ∼1 region by using the renormalization group method.View full abstractDownload PDF (174K) -
Tatsuma D. Matsuda, Yoshinori Haga, Shugo Ikeda, Andrei Galatanu, Etsu ...2005 Volume 74 Issue 5 Pages 1552-1556
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSWe have succeeded in growing a high-quality single crystal of UCu2Si2 with the tetragonal structure by the Sn-flux method and measured the electrical resistivity, magnetic susceptibility, magnetization and specific heat. UCu2Si2 is found to order antiferromagnetically below TN=106 K, and follows a successive ferromagnetic ordering at TC=100 K. The magnetic properties are highly anisotropic, reflecting the crystal structure. An easy-axis of magnetization is found to be the [001] direction (c-axis) both in the antiferromagnetic and ferromagnetic phases, while the [100] direction (a-axis) corresponds to the hard-axis in magnetization. The magnetization curve in the antiferromagnetic phase indicates a clear metamagnetic transition at a low field of about 1 kOe and changes into a ferromagnetic magnetization curve below TC=100 K. The saturation moment is determined as 1.75 μB/U at 2 K. The electronic specific heat coefficient is also determined as 20 mJ/(K2·mol).View full abstractDownload PDF (586K) -
Kiyohiro Sugiyama, Noriko Nakamura, Takeshi Yamamoto, Daisuke Honda, Y ...2005 Volume 74 Issue 5 Pages 1557-1560
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSHigh-field magnetization measurements have been performed on the filled skutterudite compounds PrFe4P12 and PrOs4Sb12 with the cubic crystal structure. Magnetization curves along the main symmetry axes of PrFe4P12 show clear anisotropy at high fields. On the basis of this result, we discuss the possible crystalline electric field (CEF) scheme in PrFe4P12 which reproduce the anisotropic feature at high magnetic fields. On the other hand, the magnetization of PrOs4Sb12 for H||⟨100⟩ at 0.1 K shows weak anomalies at 4.5 and 15 T, which correspond to the phase boundaries of the field-induced antiferroquadrupolar ordering phase. The observed magnetization curve is well explained by the CEF scheme determined by the previous neutron scattering experiments.View full abstractDownload PDF (156K) -
Noriki Terada, Takeshi Kawasaki, Setsuo Mitsuda, Hiroyuki Kimura, Yuki ...2005 Volume 74 Issue 5 Pages 1561-1565
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSWe have reinvestigated the effect of non-magnetic impurity on thermally-induced magnetic orderings in geometrically frustrated triangular lattice antiferromagnets CuFe1−xAlxO2 with x=0.00, 0.02 and 0.05, using a four-circle neutron diffractometer. Although we inferred in our previous work with a three-axis diffractometer that a proper screw type magnetic structure is realized in the intermediate-temperature (IM) phase of the samples with x=0.02 and x=0.05, in the present work we found that a sinusoidally amplitude-modulated magnetic structure with the magnetic moments canted by about 50° from the c axis toward the hexagonal ⟨1\\bar10⟩ direction is realized. These experimental findings suggest that the quasi-Ising magnetic orderings in CuFeO2 are stabilized not with the strong Ising anisotropy expected from the Ising-like successive magnetic phase transitions in CuFeO2 but with the small Ising anisotropy added to strongly competing exchange interactions.View full abstractDownload PDF (207K) -
Daisuke Okuyama, Takeshi Matsumura, Hironori Nakao, Youichi Murakami, ...2005 Volume 74 Issue 5 Pages 1566-1571
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSWe have investigated the antiferromagnetic ground state, phase IV, of TbB2C2 by resonant X-ray scattering to study the background of its anomalous magnetic structure. Polarization analysis was carried out to clarify the origin of the superlattice and forbidden reflections that appear below the Néel temperature. We observed magnetic reflections of (1 0 0.5) and (0 0 0.5), consistently with the neutron diffraction experiment by Kaneko et al. In addition, we have detected the (1 0 0) forbidden reflection in the unrotated σ–σ′ channel, which was not observed by neutron diffraction. From the detailed analysis of the resonant X-ray scattering, we conclude that this reflection originates from the ordering of the quadrupolar moment that accompany the canted antiferromagnetic structure of TbB2C2 because of the strong spin-orbit coupling. No lattice distortion was detected.View full abstractDownload PDF (288K) -
Tomohiko Nakajima, Masaki Ichihara, Yutaka Ueda2005 Volume 74 Issue 5 Pages 1572-1577
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSBy means of annealing LaBaCo2O5 under high pressure oxygen, we have successfully synthesized a new A-site ordered perovskite cobaltite, LaBaCo2O6. The structure and electromagnetic properties of LaBaCo2O6 have been investigated and compared to those of the ordinary A-site disordered La0.5Ba0.5CoO3. Both LaBaCo2O6 and La0.5Ba0.5CoO3 have mixed states of low-spin and intermediate-spin states and show metallic behaviors generated by double exchange interaction. LaBaCo2O6 has a ferromagnetic transition at TC=175 K, which is lower by 15 K than TC of La0.5Ba0.5CoO3. At around 140 K, some structural changes are observed in both compounds and below the temperature they exhibit magnetic glassy (cluster glass) behaviors, accompanied by the gradual change to insulating or simiconductive behaviors. The refined structural data and magnetic and electrical properties suggest a partial dx2−y2 orbital ordering for LaBaCo2O6 below 140 K, in contrast to a partial d3z2−r2 orbital ordering for La0.5Ba0.5CoO3.View full abstractDownload PDF (487K) -
Masaaki Matsuda, Kazuhisa Kakurai, Mohana Yethiraj, Kunihiko Oka2005 Volume 74 Issue 5 Pages 1578-1581
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSCa2Y2Cu5O10 is a quasi-one-dimensional magnet, which consists of the ferromagnetic edge-sharing CuO2 chains. It was previously reported from neutron inelastic scattering experiments in Ca2Y2Cu5O10 up to ∼14 meV that in the magnetically ordered state there is an anomalous broadening of spin-wave excitations along the chain, which is caused mainly by the antiferromagnetic interchain interactions [M. Matsuda et al.: Phys. Rev. B 63 (2001) 180403(R)]. In this study we extended an energy range of the measurement up to ∼25 meV. The experimental result suggests that there exist two excitation modes, which is consistent with a theoretical result qualitatively. One mode corresponds to the relatively sharp spin-wave excitations, which broaden with increasing qchain and disappear around qchain∼0.2 r.l.u. and ω∼10 meV. Another one corresponds to the very broad excitations apparent at qchain∼0.2–0.3 r.l.u. and ω∼12–25 meV.View full abstractDownload PDF (142K) -
Andrei Galatanu, Yoshinori Haga, Tatsuma D. Matsuda, Shugo Ikeda, Etsu ...2005 Volume 74 Issue 5 Pages 1582-1597
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSWe investigated the magnetic property of typical uranium compounds by measuring the magnetic susceptibility in an extended temperature range up to about 800 K. The magnetic susceptibility follows the Curie–Weiss law for a localized 5f2-electron compound UPd3 and a ferromagnetic insulator UFe4P12. In most of the investigated compounds we observed a crossover effect of the 5f electrons from a low-temperature itinerant nature to a high-temperature localized one. This is found to be characteristic for ferromagnetic superconductors such as UGe2 and UIr, and also for antiferromagnets like USb2 or UNiSb2. To assess an extension of this characteristic property in the uranium compounds we also investigated typical 5f-itinerant compounds like UGa3 and UPtGa5. The crossover effect is essentially important in heavy fermion compounds such as UPt3, UPd2Al3 and URu2Si2. Even in the paramagnetic compound of UB4, the magnetic susceptibility is not temperature-independent, but approaches a 5f-localized tendency at high temperatures. Since the samples were single crystals, we were also able to trace the evolution of the magnetic anisotropy. The high-temperature anisotropic susceptibility data were analyzed on the basis of the crystalline electric field scheme.View full abstractDownload PDF (2839K) -
Koichi Katsumata, Akiko Kikkawa, Yoshikazu Tanaka, Susumu Shimomura, S ...2005 Volume 74 Issue 5 Pages 1598-1601
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSNon-resonant X-ray Bragg diffraction measurements on a small, single crystal of α-Gd2S3 in zero and non zero applied magnetic fields are reported. From independent neutron diffraction measurements, the magnetic unit cell is found to be the same as the chemical unit cell. Therefore, the observation of magnetic X-ray diffraction by this compound is particularly challenging. We observe a change in the intensity around the Néel temperature in zero field, as well as around the phase boundaries at finite magnetic fields. The X-ray diffraction intensity is calculated based on the previously established magnetic structure. A reasonable amount of intensity from the interference between magnetic and charge scattering is predicted, and it provides a satisfactory account of our observations.View full abstractDownload PDF (167K) -
Tomohito Nakano, Hirohumi Yamashiro, Kaoru Fujita, Shigeyuki Murayama2005 Volume 74 Issue 5 Pages 1602-1608
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSSusceptibility measurements have been performed on polycrystalline samples Ce1−yRy(Ru0.85Rh0.15)2Si2 (R = Sc, La) in order to clarify the chemical pressure effect for the SDW in the heavy fermion Ce(Ru0.85Rh0.15)2Si2. Lattice parameters a and c both decrease with increasing Sc concentration and increase with increasing La concentration. For Ce1−yScy(Ru0.85Rh0.15)2Si2 system, the Néel temperature TN decreases with increasing Sc concentration and disappears for y≥0.2. We observed the Curie–Weiss law in the susceptibility at high temperature and a tendency of the saturation in the low temperature susceptibility. The tendency of the saturation and the Weiss temperature Θ determined from the high temperature susceptibility increase with increasing Sc concentration. These facts can be explained through the increase of the c–f hybridization and itinerancy of the f electron. For Ce1−yLay(Ru0.85Rh0.15)2Si2 system, the TN slightly decreases with increasing La concentration and the tendency of the saturation becomes weaker with increasing y and is no more observed down to TN for y>0.15. The Θ rapidly decreases with increasing La concentration and becomes almost zero for y>0.15. These facts suggest that the c–f hybridization becomes weak with increasing y and that the itinerant AF phase for y<0.15 is replaced by the AF phase with the localized moment for y>0.15. The Kondo temperature TK estimated from Θ is scaled by a single proportional function of the lattice parameter c in both cases for the Sc and La substitution.View full abstractDownload PDF (216K) -
S. N. Azizi, A. A. Rostami, A. Godarzian2005 Volume 74 Issue 5 Pages 1609-1620
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSHartree–Fock self-consistent-field (HF-SCF) theory and the Gauge-including atomic orbital (GIAO) methods are used in the calculation of 29Si NMR chemical shifts for ABOUT 90 units of 19 compounds of various silicate species of precursors for zeolites. Calculations have been performed at geometries optimized at the AM1 semi-empirical method. The GIAO-HF-SCF calculations were carried out with using three different basis sets: 6-31G*, 6-31+G** and 6-311+G(2d,p). To demonstrate the quality of the calculations the calculated chemical shifts, δ, were compared with the corresponding experimental values for the compounds in study. The results, especially with 6-31+g** are in excellent agreement with experimental values. The calculated chemical shifts, in practical point of view, appear to be accurate enough to aid in experimental peak assignments. The difference between the experimental and calculated 29Si chemical shift values not only depends on the Qn units but also it seems that basis set effects and the level of theory is more important. For the series of molecules studied here, the standard deviations and mean absolute errors for 29Si chemical shifts relative to TMS determined using Hartree–Fock 6-31+G** basis is nearly in all cases smaller than the errors for shifts determined using HF/6-311+G(2d,p).View full abstractDownload PDF (232K) -
Masahiro Ueda, Hitoshi Suzuki, Osamu Kido, Masayuki Shintaku, Mami Kur ...2005 Volume 74 Issue 5 Pages 1621-1624
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSIndium sulfide particles produced in smoke have been analyzed by transmission electron microscopy. Three phases, α, β and β′ with the different external shapes were produced. A mixture phase of β and β′ was found and the lattice relation was elucidated. The phase transition temperatures were assigned to be 400°C (α to β) and 500°C (β′ to β).View full abstractDownload PDF (427K) -
Atsuyoshi Shimamoto, Takeshi Fujiwara, Atsushi Iwamae, Takashi Fujimot ...2005 Volume 74 Issue 5 Pages 1625-1628
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSWe have irradiated vapor-deposited CuCl films and bulk CuCl at 4.6 K with picosecond light pulses of 82 MHz repetition rate at the photon energy of 3.29 eV. Exciton luminescence having longitudinal optical (LO) phonon structures appeared in the time scale of an hour. Temperature dependences of the intensities of this luminescence and the I1 luminescence suggested that both the luminescence bands quenched by thermal activation from the relevant bound exciton states to the Z3 exciton state.View full abstractDownload PDF (92K) -
Yukio Saito, Hiroyuki Hyuga2005 Volume 74 Issue 5 Pages 1629-1635
Published: May 15, 2005
Released on J-STAGE: December 13, 2007
JOURNAL RESTRICTED ACCESSAs an attempt to understand the homochirality of organic molecules in life, a chemical reaction model is proposed where the production of chiral monomers from achiral substrate is catalyzed by the polymers of the same enatiomeric type. This system has to be open because in a closed system the enhanced production of chiral monomers by enzymes is compensated by the associated enhancement in back reaction, and the chiral symmetry is conserved. Open flow without cross inhibition is shown to lead to the chirality selection in a general model. In polymerization, the influx of substrate from the ambience and the efflux of chiral products for purposes other than the catalyst production make the system necessarily open. The chiral symmetry is found to be broken if the influx of substrate lies within a finite interval. As the efficiency of the enzyme increases, the maximum value of the enantiomeric excess approaches unity so that the chirality selection becomes complete.View full abstractDownload PDF (185K)