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Volume 75, Issue 2
Displaying 1-44 of 44 articles from this issue
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Kimiaki Konno, Hiroshi Kakuhata2006 Volume 75 Issue 2 Pages 023001
Published: February 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSA generalization of the localized induction equation is presented where the generalized equation is integrable and permits the solutions of the stretched vortex filament. Further generalizations are presented.View full abstractDownload PDF (50K) -
Jorge A. González, Leonardo Trujillo2006 Volume 75 Issue 2 Pages 023002
Published: February 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSWe show that any string xs,xs+1,…,xs+r (for any r) constitutes a set of statistically independent random variables given the generalized chaotic sequence xn=cos[2πθzn], where z is a typical real number. This result can be generalized to sequences of type xn=P(zn), where P(t) is a periodic function. We will discuss the relevance of this result to dynamical systems, real physical experiments, and new technological devices used in secure communications.View full abstractDownload PDF (7408K) -
D. Pasqualini, H. Koguchi, G. Spizzo, Y. Yagi, Y. Hirano, P. Martin, H ...2006 Volume 75 Issue 2 Pages 023501
Published: February 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSThe MHD instabilities that sustain the reversed-field pinch (RFP) configuration tend to phase-lock together and also to wall-lock, forming a bulging of the plasma column, called “locked mode”. This phenomenon is of particular interest, since the locked mode causes a larger plasma resistivity, plasma cooling, and, in some cases, anomalous discharge termination. Up to now, studies of the locked mode have been focused on m=1 modes (being m the poloidal mode number). In this Letter we show that m=0 modes also play a role, based on the cross-check between magnetic spectra and toroidally resolved Dα array measurements.View full abstractDownload PDF (946K) -
Haruka Abe, Yu Saitoh, Tetsuto Ueda, Futoshi Ogasawara, Ryuji Nomura, ...2006 Volume 75 Issue 2 Pages 023601
Published: February 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSVery fast growth of the c-facet of a 4He crystal was induced by acoustic waves. The growth velocity was larger at lower temperatures and saturated below about 400 mK. The velocity was proportional to the acoustic wave power. This fast growth cannot be explained by the spiral growth mechanism for the known value of the step mobility. We developed a step multiplication model for high-power acoustic waves and found reasonable agreement with the observed temperature and power dependence of the growth velocity.View full abstractDownload PDF (102K) -
Noriki Terada, Setsuo Mitsuda, Hiroyuki Ohsumi, Keisuke Tajima2006 Volume 75 Issue 2 Pages 023602
Published: February 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSWe have performed synchrotron radiation X-ray diffraction measurements on a triangular lattice antiferromagnet CuFeO2, using the single crystal. The crystal lattice symmetry lowers from hexagonal to orthorhombic below the magnetic phase transition (from a partially disordered phase to four-sublattice phase) temperature TN2. In addition, superlattice reflections were observed below TN2; this suggests that the “scalene triangle model” lattice distortion splits the nearest neighbor exchange interaction in the basal plane into three different exchange interactions. This distortion lifts the vast degeneracy of the strongly frustrated spin system, leading to the four-sublattice ground state. Thus we argue that the lattice degree of freedom plays an important role in the stabilization of the four-sublattice ground state in CuFeO2.View full abstractDownload PDF (554K) -
Ko-ichi Magishi, Yusuke Nakai, Kenji Ishida, Hitoshi Sugawara, Ikuko M ...2006 Volume 75 Issue 2 Pages 023701
Published: February 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSWe report the results of 121,123Sb-nuclear quadrupole resonance (NQR) and 139La-NMR measurements on a filled skutterudite antimonide LaFe4Sb12 in order to investigate the magnetic properties at low temperatures from a microscopic point of view. The nuclear spin–lattice relaxation time T1 of Sb nuclei deviates from the relation T1T = constant above 4.2 K, where 1⁄T1T has a Curie–Weiss temperature dependence 1⁄T1T=C⁄(T+θ) with θ∼30 K. The temperature dependence of the Knight shift of 139La nuclei, which is related to the susceptibility at q=0, is scaled to that of 1⁄T1T above 40 K. This relation strongly suggests that ferromagnetic fluctuations are predominant in LaFe4Sb12. We also point out that LaFe4Sb12 is situated close to the ferromagnetic instability due to the small Weiss temperature in the Curie–Weiss behavior of 1⁄T1T and the Knight shift.View full abstractDownload PDF (444K) -
Kenichi Tenya, Shingo Yasuda, Makoto Yokoyama, Hiroshi Amitsuka, Kazuh ...2006 Volume 75 Issue 2 Pages 023702
Published: February 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSWe report on detailed measurements of the magnetization of Sr2RuO4 in the superconducting mixed state, performed on a high-quality single crystal in a magnetic field parallel to the [100] axis. A small but distinct kink structure is found at around 9 kOe in the magnetization curve, indicating the presence of an additional superconducting phase transition that has been theoretically predicted to be evidence of the superconductivity with a two-component order parameter. An anomalous increase of magnetization is also observed just below the upper critical field. These anomalies disappear when the field is tilted from the [100] axis by only 3–5°. Possible origins of such magnetization behavior are discussed from the viewpoint of a spin-triplet pairing scenario with a two-component order parameter.View full abstractDownload PDF (381K) -
Hidekazu Okamura, Masato Matsubara, Koichiro Tanaka, Kazutoshi Fukui, ...2006 Volume 75 Issue 2 Pages 023703
Published: February 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSInfrared absorption spectra of SrTiO3 have been measured under above-band-gap photoexcitations to study the properties of photogenerated carriers, which should play important roles in previously reported photoinduced phenomena in SrTiO3. A broad absorption band appears over the entire mid-infrared region under photoexcitation, which is attributed to absorption by the photogenerated carriers occupying in-gap states. The photoinduced absorption is strongly dependent on temperature even below 35 K, where the average photocarrier density is nearly constant. The data show that the density of in-gap states occupied by the photocarriers is high and distributed over a wide energy range extending to the band edges.View full abstractDownload PDF (173K) -
Yoshihiko Okamoto, Minoru Nohara, Fumiko Sakai, Hidenori Takagi2006 Volume 75 Issue 2 Pages 023704
Published: February 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSTransport and thermal properties were examined for the layered rhodium oxide β-Sr1−xRh2O4. The parent compound SrRh2O4 is a band insulator. The introduction of Sr deficiencies results in an insulator–metal transition around x\\simeq0.2. The metallic phase for x>0.2 is a strongly correlated Fermi liquid with an enhanced quasiparticle mass. The enhanced thermoelectric power of S∼150 μV/K at 1000 K in this metallic phase suggests a potential of Sr1−xRh2O4 as a thermoelectric material.View full abstractDownload PDF (172K) -
Y. Nakajima, K. Izawa, Y. Matsuda, K. Behnia, H. Kontani, M. Hedo, Y. ...2006 Volume 75 Issue 2 Pages 023705
Published: February 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSWe report on the pressure dependence of the Hall coefficient RH in quasi-2D heavy fermion CeCoIn5. At ambient pressure, below a temperature associated with the emergence of non-Fermi liquid properties, RH is anomalously enhanced. We found that the restoration of the Fermi liquid state with applied pressure leads to a gradual suppression of this dramatic enhancement. Moreover, the enhancement in RH was found to be confined to an intermediate temperature window, where inelastic electron–electron scattering is dominant. Our results strongly support the presence of cold and hot spots on the Fermi surface probably due to anisotropic scattering by antiferromagnetic fluctuations, which may also prove relevant for the debate on the anomalous normal-state properties of high-Tc cuprates.View full abstractDownload PDF (201K) -
Yositake Takane2006 Volume 75 Issue 2 Pages 023706
Published: February 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSCharge imbalance relaxation in s-wave superconductors is studied when temperature T is much lower than the transition temperature Tc. Although the charge imbalance conversion near Tc is mainly caused by inelastic phonon scattering, it becomes less dominant with decreasing T. We study the charge imbalance conversion resulting from elastic impurity scattering in combination with pairing anisotropy. We determine the corresponding conversion time and demonstrate that the elastic process dominates the inelastic phonon process when T<<Tc. A qualitative picture of the charge imbalance relaxation is presented based on the conversion time and the energy relaxation time due to inelastic phonon scattering.View full abstractDownload PDF (114K) -
K. Ohgushi, H. Gotou, T. Yagi, Y. Ueda2006 Volume 75 Issue 2 Pages 023707
Published: February 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSPolycrystals of orthorhombic CuRh2O4 were prepared by a solid state reaction under high pressure and its magnetic properties were compared with those of polymorph–tetragonal CuRh2O4 (spinel-type compound). The orthorhombic phase undergoes antiferromagnetic transition at 24 K. The ratio of the Curie–Weiss temperature (θCW) to the Néel temperature (TN) is estimated to be f=|θCW|⁄TN=2.6 and is considerably smaller than f in the tetragonal phase, 5.3. This indicates that geometrical magnetic frustration inherent in the Cu2+ network of the spinel structure is released in the orthorhombic phase with lower crystal symmetry. We observed a weak ferromagnetism below TN in the orthorhombic phase; this is also discussed in terms of crystal symmetry.View full abstractDownload PDF (280K) -
Shinya Katayama, Akito Kobayashi, Yoshikazu Suzumura2006 Volume 75 Issue 2 Pages 023708
Published: February 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSElectric conductivity that reveals the zero-gap semiconducting (ZGS) state has been investigated as a function of temperature T and lifetime τ in order to understand the ZGS state in a quarter-filled α-(BEDT-TTF)2I3 salt with four sites in the unit cell. By treating τ as a parameter and employing the one-loop approximation, it is found that the conductivity is proportional to T and τ for kBT>>h⁄τ and is independent of T and τ for kBT<<h⁄τ. Further, the conductivity, which is independent of T in the ZGS state, is examined for the impurity scattering in terms of the Born approximation.View full abstractDownload PDF (130K) -
Hirono Kaneyasu, Keita Kishigi, Yasumasa Hasegawa2006 Volume 75 Issue 2 Pages 023709
Published: February 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSThe effect of electron correlation on the angle dependence of magnetoconductivity is studied in quasi-one-dimensional organic conductors. We investigated the effect on the basis of the momentum dependence of both quasi-particle’s lifetime and velocity near the spin-density-wave (SDW). We found that the momentum dependence of quasi-particle’s lifetime mainly governs the angle dependence of one-dimensional axis magnetoconductivity. On the other hand, the change in velocity originating from the electron correlation gives the dominant effects on the angle dependence of the interchain axis magnetoconductivity. The effect of electron correlation is clarified from the association of the momentum dependences of lifetime and velocity with the momentum dependences of commensurate orbitals on a Fermi surface in magnetic fields.View full abstractDownload PDF (336K) -
Yasunori Tominaga, Yuko Amo2006 Volume 75 Issue 2 Pages 023801
Published: February 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSLow-frequency Raman spectra of liquid water from −250 to 250 cm−1 towards to and above the supercritical point have been observed and analyzed by using the multiple random telegraph model (MRT) relaxation function. The 180 cm−1 band has vanished with increasing temperature with constant pressure at 25 MPa. This is due to the destruction of hydrogen-bonds. The obtained relaxation time first decreases and then increases from about 260°C (433 K) with increasing temperature toward to the supercritical state. This behavior is consistent with that of the dielectric relaxation time.View full abstractDownload PDF (143K) -
Akira Asai, Katsuhiko Shinjo, Seiji Miyashita2006 Volume 75 Issue 2 Pages 024001
Published: February 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSBy making use of a simulation scheme incorporating the Navier–Stokes equation and the van der Waals equation, we study the combined dynamics of fluid motion and phase separation in a bubble generation process. The thermodynamic force for phase separation is taken into account by the entropy density of the van der Waals fluid, which is a function of local density and local energy. With this force and the surface tension, explicit forms of equations of motion are given for the density, momentum, and energy. In this scheme, we are able to treat gas and liquid states in a unified way and study a spontaneous bubble generation process by heating. In this paper, we demonstrate the processes of bubble generation in a pinpoint-heated one-dimensional system of water, and study their characteristics. For example, before the bubble generation, a step-like pressure domain wall propagates from the the position where the liquid is heated. After further heating, thermodynamic instability takes place and a gas region is generated and expands. The temperature and pressure profiles around the domain boundary are investigated when the gas region is expanding. The conditions of the heating process for bubble generation are also studied.View full abstractDownload PDF (329K) -
Takeya Tsurumi2006 Volume 75 Issue 2 Pages 024002
Published: February 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSPropagation of ultrashort electromagnetic pulses of few- to sub-cycle duration is studied. Assuming that the spectrum of the pulse is localized at zero frequency enough to be weakly dispersive, a paraxial equation for the electric field is derived, which has axially symmetric gaussian beam mode solutions. Then, the pulse is found to propagate with its shape unchanged within certain propagation distance determined by dispersion and dissipation strength of the media and the bandwidth of the pulse’s initial spectrum. On the other hand, for the pulse propagating sufficiently long distance, where the dispersion plays a main role, the asymptotic behavior of the oscillatory damped tail of the pulse is investigated. As a possible application, propagation of phonon–polariton pulses in polar crystals including LiNbO3 is considered.View full abstractDownload PDF (162K) -
Seiji Miyoshi, Masato Okada2006 Volume 75 Issue 2 Pages 024003
Published: February 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSIn the framework of on-line learning, a learning machine might move around a teacher due to the differences in structures or output functions between the teacher and the learning machine or due to noises. The generalization performance of a new student supervised by a moving machine has been analyzed. A model composed of a fixed true teacher, a moving teacher and a student that are all linear perceptrons with noises has been treated analytically using statistical mechanics. It has been proven that the generalization errors of a student can be smaller than that of a moving teacher, even if the student only uses examples from the moving teacher.View full abstractDownload PDF (130K) -
Norio Inui2006 Volume 75 Issue 2 Pages 024004
Published: February 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSThe influence of optical adsorption on the Casimir force acting between a metallic sphere and a semiconductive plate illuminated with Gaussian light beam is considered. The Casimir torque and the lateral Casimir force result form the inhomogeneous photonionization. Taking into account the spatial inhomogeneousness of the plasma frequency in the semiconductive plate, the dependence of the Casimir force on the distance between the optical axis and the center of the sphere is computed within the proximity force approximation.View full abstractDownload PDF (132K) -
Atsushi Kamimura, Satoshi Yukawa, Nobuyasu Ito2006 Volume 75 Issue 2 Pages 024005
Published: February 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSAs a first step to study reaction dynamics in far-from-equilibrium open systems, we propose a stochastic protocell model in which two mutually catalyzing chemicals are replicating depending on the external flow of energy resources J. This model exhibits an Arrhenius type reaction; furthermore, it produces a non-Arrhenius reaction that exhibits a power-law reaction rate with regard to the activation energy. These dependences are explained using the dynamics of J; the asymmetric random walk of J results in the Arrhenius equation and conservation of J results in a power-law dependence. Further, we find that the discreteness of molecules results in the power change. Effects of cell divisions are also discussed in our model.View full abstractDownload PDF (210K) -
Takahiro Murakami, Yositake Takane2006 Volume 75 Issue 2 Pages 024006
Published: February 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSThe pulse control of decoherence in a qubit interacting with a quantum environment is studied with focus on a general case where decoherence is induced by both pure dephasing and population decay. To observe how the decoherence is suppressed by periodic π pulses, we present a simple method to calculate the time evolution of a qubit under arbitrary pulse sequences consisting of bit-flips and/or phase-flips. We examine the effectiveness of the two typical sequences: bb sequence consisting of only bit-flips, and bp sequence consisting of both bit- and phase-flips. It is shown that the effectiveness of the pulse sequences depends on a relative strength of the two decoherence processes especially when a pulse interval is slightly shorter than qubit–environment correlation times. In the short-interval limit, however, the bp sequence is always more effective than, or at least as effective as, the bb sequence.View full abstractDownload PDF (180K) -
Akira Narita, Masahiko Higuchi2006 Volume 75 Issue 2 Pages 024301
Published: February 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSThe simple and tractable representation for the LS-multiplet energy in l1l2-configuration in an atom is derived in the form of the polynomials being a function of l1·l2 which obey the recurrence formulae, and is suitable for the vector model. Moreover, it is extended to ln configurations. On a basis of the model, the definition of the orbital polarization energy is given. The more precise expressions of the energies compared to those so far proposed by Eriksson et al. are derived for the maximal spin multiplets in pn, dn, and fn. They are composed of two terms depending on −3L2⁄2 and n(n−2l−1). They are the exact for pn and dn, but it for fn is correct only for a ground multiplet. Other expressions are also derived as a function of L2 for fn, though more complicated. For the actual atomic and band structure calculations based on local-spin-density-approximation (LSDA), the modified expression for the energy is proposed. The potential is derived from its expression in terms of the density functional theory, and can be applied to their structure calculations.View full abstractDownload PDF (191K) -
Nobuaki Ikuta, Akihide Takeda2006 Volume 75 Issue 2 Pages 024501
Published: February 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSProcedures for obtaining the transport properties of electrons in gas under a uniform electric field by traditional methods are compared with those by the flight time integral (FTI) method such that they conform to the two comment papers on the FTI method given by Kumar and Robson in 1995. The most important difference between traditional and FTI methods is that the starting rate distribution Ψs(v0) is adopted in FTI as the principal unknown function instead of the velocity distribution in flight f(c), which has always been used in traditional theories. The use of Ψs(v0) has advantages not only in the possibility of obtaining accurate transport coefficients but also in providing a deeper understanding of them based on the full flight data of electrons.View full abstractDownload PDF (129K) -
Vu Van Hung, Jaichan Lee, K. Masuda-Jindo, P. T. T. Hong2006 Volume 75 Issue 2 Pages 024601
Published: February 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSThe process of self-diffusion in semiconductors at high pressure is studied using the statistical moment method including the anharmonicity effects of the lattice vibration. The activation energy, Q, and pre-exponential factor, D0, of the self-diffusion coefficient are given in an explicit form. The thermodynamic relationships so obtained permit the direct calculation of the activation energy, Q, and pre-exponential factor, D0, in Si at high pressure, both in the high temperature region near the melting temperature, and at low (room temperature) temperatures. The calculated results are shown to be in good agreement with the experimental data.View full abstractDownload PDF (122K) -
Sachiko T. Nakagawa, Masaya Iwatani, Gerhard Betz2006 Volume 75 Issue 2 Pages 024602
Published: February 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSWe have studied the coalescence mechanism of impurity atoms implanted into a crystalline target at low temperatures, paying attention to the dimer formation mechanism. A classical molecular-dynamics (MD) calculations was used in the case of 1 keV B ion implantation at 100 K into a crystalline silicon (c-Si) target that was supersaturated with pre-embedded B atoms at a concentration of 3 at. %. The initial phase of dimer formation was investigated in terms of the temperature distribution and the degradation of the long-range order (LRO) parameters defined in the pixel mapping (PM) method. One result was the locally high temperature and big temperature gradient that revealed the acceleration of collisional diffusion of light impurity atoms in the host medium. The other finding was the decrease of the LRO parameters. This fact associated with the number of self-interstitial atoms (SIAs) implies a deformed potential-field in a crystal under ion irradiation. These results indicate that dynamically enhanced diffusion or collisional-diffusion is the origin of dimer formation.View full abstractDownload PDF (277K) -
Yusuke Hiejima, Mitsuhiro Kanakubo, Yoshihiro Takebayashi, Takafumi Ai ...2006 Volume 75 Issue 2 Pages 024603
Published: February 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESS129Xe NMR spectroscopy is applied for direct observation of Xe confined in the porous Vycor glass. The chemical shifts of bulk and confined Xe are obtained simultaneously in a wide range of density from the gas phase to the liquid phase, including the supercritical region. The temperature and pressure dependences of the chemical shift of confined Xe are different from those of bulk Xe, which are approximately expressed by a linear function of bulk density. The phase transition of confined Xe is detected by the chemical shift, of which the pressure dependence along isotherms shows hysteresis loops.View full abstractDownload PDF (146K) -
Ananda Kumar Das, Reo Nakamura, Miwako Takahashi, Hiroshi Iwasaki, Toe ...2006 Volume 75 Issue 2 Pages 024604
Published: February 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSX-ray and electron diffraction measurements were performed to investigate the structure and ordering behaviour of the ternary alloys CuMPt6 (M=Ti, V, Cr, Mn, Fe, Co, and Ni). X-ray polycrystalline diffraction patterns of all the specimens quenched from 1000°C have shown that a single phase is formed at this stoichiometric composition. The alloys with M=Cr, Mn, Co, and Ni have the face-centred cubic (fcc) structure, while in the alloys with M=Ti, V, and Fe ordering has occurred and the structure is of the Cu3Au type. On annealing at lower temperatures ordering has been induced in the alloys with M=Cr, Mn, and Co and the structure is of the Cu3Au type, though the ordering in the last alloy has remained incomplete. Detailed X-ray diffraction measurements on single crystals of the CuMnPt6 alloy have revealed that further ordering takes place and structure changes from the Cu3Au type into the cubic ABC6 type with the unit cell as large 2×2×2 as the fcc unit cell, a new observation of the double-step ordering in the ternary fcc alloy. The corresponding transition temperatures are Tc=970(±5)°C and Tcl=750(±5)°C.View full abstractDownload PDF (293K) -
Susumu Fujiwara, Masato Hashimoto, Takashi Itoh, Hiroaki Nakamura2006 Volume 75 Issue 2 Pages 024605
Published: February 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSThe structure formation of a single polymer chain in solution with explicit solvent molecules is investigated by molecular dynamics simulation. The orientationally ordered structure is formed at a low temperature by quenching from a random conformation at a high temperature. The growth of the global and local orientational order proceeds in a stepwise manner at T≥350 K, whereas it proceeds in a gradual manner at T=300 K. From the detailed analyses of the parallel ordering process, it is found that a conformational change of the polymer chain occurs at first, and then parallel ordering starts to take place. In comparison with the simulation results of an isolated polymer chain in vacuum, it is ascertained that the stem length of the orientationally ordered structure formed in solution becomes 2–3 times longer than that formed in vacuum.View full abstractDownload PDF (379K) -
Kenji Ohwada, Kazuma Hirota, Hikaru Terauchi, Hidehiro Ohwa, Naohiko Y ...2006 Volume 75 Issue 2 Pages 024606
Published: February 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSStructural properties of as-grown Pb(In1⁄2Nb1⁄2)O3 (PIN) single crystals at room temperature (RT) were investigated by x-ray and neutron scattering techniques, taking much account of the difference in the penetration depth and spatial resolution of x-rays and those of neutrons. A strong diffuse scattering was observed by x-ray while h⁄4k⁄40 superlattice reflections were found by neutron, indicating a relaxor state in the outer-layer of the crystal and an antiferroelectric (AFE) state in the bulk. The phonon dispersion was measured for the first time for the PIN series. Two transverse optic (TO1 and TO2) modes were clarified near the zone center though neither water-fall behavior nor folding of phonon branches was confirmed. We have thus concluded that a major part of the as-grown PIN crystal at RT is ferroelectric (FE). These results imply that the B-site chemical ordering, i.e., inhomogeneity, which controls the structural properties of PIN, is unevenly distributed throughout the crystal. We speculate that small AFE grains coexist with the FE matrix while the outer-layer is in a relaxor state in the as-grown PIN.View full abstractDownload PDF (420K) -
Syuma Yasuzuka, Keizo Murata, Masahiro Shimotori, Tsutomu Fujimoto, Ju ...2006 Volume 75 Issue 2 Pages 024701
Published: February 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSThis paper reports the pressure effect on resistivity in the quasi two-dimensional (2D) organic conductor (DOET)2BF4 with orientational disorder of BF4 anions. At ambient pressure, the resistivity shows metal–insulator transition at 80 K and 2D variable range hopping (VRH) conduction below 80 K. The insulating behavior is suppressed by applying pressure and the temperature dependence of the resistivity shows the crossover from the 2D VRH to the logarithmic divergence as applied pressure increases. From the observation of the positive magnetoresistance, the logarithmic divergence of the resistivity is not attributed to the Anderson localization, but to the effect of the electron–electron interaction. This crossover is simply understood in terms of the screening effect on the random potential by increase of bandwidth due to applied pressure. It is found that a value of sheet conductance at low temperatures above 8 kbar, where the insulating state is almost suppressed, approaches to the minimum conductivity for a metallic state, σmin=e2⁄h=1⁄(25.8kΩ), first proposed by Mott.View full abstractDownload PDF (292K) -
Kazufumi Suenaga, Gendo Oomi, Takeshi Sakai, Kesami Saito, Koki Takana ...2006 Volume 75 Issue 2 Pages 024702
Published: February 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSThe effect of pressure and magnetic field on the temperature dependent electrical resistivity ρ(T) of the [Co(1.02 nm)/Cu(tCu nm)]25 magnetic multilayers (MML) with tCu=0.76 [ferromagnetic (F)] and 1.05 [antiferromagnetic (AF)] has been investigated at low temperature. MR ratio Δρ⁄ρs for tCu=1.05 and 0.76 decreases with increasing pressure. The pressure dependent Δρ⁄ρs for tCu=1.05 is more significant than that for 0.76. ρ(T) at H=0 and above saturation field Hs (H=2 T) for Co/Cu MMLs is found to show T2-dependence in the relatively wide temperature range, 4.2≤T≤20 K, at low temperature. The coefficient of T2 term (=A) for F-state is larger than that for AF-state at ambient pressure. The change of A for tCu=1.05 at H=0 is smaller than that at H=2 T. These results are discussed on the basis of the electron scattering at interfaces due to magnons or spin-wave.View full abstractDownload PDF (268K) -
Hidekatsu Suzuura, Tsuneya Ando2006 Volume 75 Issue 2 Pages 024703
Published: February 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSThe weak-localization correction to the Boltzmann conductivity due to impurity scattering is calculated in metallic carbon nanotubes within the effective-mass approximation. The correction is positive for the impurity with interaction range larger than the lattice constant, while the impurity with shorter interaction length turns the correction into a negative value destroying the anti-localization. The crossover from anti-localization to weak localization is realized by controlling the coherence time.View full abstractDownload PDF (140K) -
Tetsuo Okane, Jun Okamoto, Kazutoshi Mamiya, Shin-ichi Fujimori, Yukih ...2006 Volume 75 Issue 2 Pages 024704
Published: February 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSX-ray absorption magnetic circular dichroism (XMCD) at the U N4,5 edges was measured for the ferromagnetic superconductor UGe2 in the normal state. The orbital and spin magneic moments deduced from the sum rule analysis of the XMCD data indicate that the U atom in UGe2 is considered to be closer to the trivalent state rather than the tetravalent state. The temperature dependence of the XMCD signal does not show any significant anomaly at T*∼30 K, where the resistivity anomaly was observed at ambient pressure. The XMCD measurement at the U N2,3 edge indicates that the U 6d electrons have negligibly small magnetic contributions.View full abstractDownload PDF (177K) -
Soichiro Shibasaki, Ichiro Terasaki2006 Volume 75 Issue 2 Pages 024705
Published: February 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSWe prepared polycrystalline samples of R2PdO4 (R = La, Nd, Sm, and Gd) using a NaCl flux technique. The measured resistivity is of the order of 103–104 Ω cm at room temperature, which is two orders of magnitude smaller than those reported so far. We also studied the substitution effects of Ce for Nd in Nd1.9Ce0.1PdO4, where the substituted Ce decreases resistivity and the magnitude of thermopower. Activation energy gap of 70–80 meV and an effective mass of 15 evaluated from the measured data are suitable for thermoelectric materials, but a mobility of 10−6 cm2/(V·s) is much lower than typical mobilities of 1–10 cm2/(V·s) for other thermoelectric oxides.View full abstractDownload PDF (218K) -
Takeshi Toshima, Katsuhiko Inagaki, Noriyuki Hatakenaka, Satoshi Tanda2006 Volume 75 Issue 2 Pages 024706
Published: February 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSWe discover a supercluster of electrons in the ultrathin TaSe2 crystals synthesized by our developed de-chalcogenide method. The supercluster has an unexpected structure containing 61 electrons denoted by \\sqrt61×\\sqrt61, in addition to a \\sqrt49×\\sqrt49 supercluster based on \\sqrt7×\\sqrt7 clusters expected in triangle lattices. This new hierarchal structure and successive clustering cannot be explained by a conventional electron clustering mechanism assisted by background lattice distortions, i.e., charge-density-wave formation mechanism based on Fermi surface nesting. We propose an alternative possible formation mechanism based on saddle-point nesting, taking into account a trigonal symmetry as well as lattice distortion energy.View full abstractDownload PDF (795K) -
Tsuneya Ando2006 Volume 75 Issue 2 Pages 024707
Published: February 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSBecause of the presence of two valleys and the electron spin, the exciton states have a degeneracy of 16 in the lowest order k·p approximation. Due to a weak short-range part of the Coulomb interaction, they are split into several levels, leaving only a single optically-active bright level and making all others optically-inactive or dark. Their ordering and energy splitting are shown to be determined by two parameters characterizing the short-range interaction, sensitive to detailed form of the potential and wave function. The presence of a magnetic flux through the cross section, accessible experimentally, modifies these energy levels strongly and causes the appearance of two bright excitons.View full abstractDownload PDF (1351K) -
Yoichi Nishiwaki, Norikazu Todoroki2006 Volume 75 Issue 2 Pages 024708
Published: February 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSWe study the lattice–spin model of RbCoBr3 which is proposed by Shirahata and Nakamura, by mean field approximation. This model is an Ising spin system on a distorted triangular lattice. There are two kinds of frustrated variables, that is, the lattice and spin. We obtain a phase diagram of which phase boundary is drawn continuously in a whole region. Intermediate phases that include a partial disordered state appear. The model has the first-order phase transitions in addition to the second-order phase transitions. We find a three-sublattice ferrimagnetic state in the phase diagram. The three-sublattice ferrimagnetic state does not appear when the lattice is not distorted.View full abstractDownload PDF (128K) -
Haruhiro Higaki, Isao Ishii, Daisuke Hirata, Moo-Sung Kim, Toshiro Tak ...2006 Volume 75 Issue 2 Pages 024709
Published: February 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSElastic moduli, specific heat, magnetic susceptibility and electrical resistivity have been measured for single-crystalline Kondo compounds CeRhIn and CeRhSn with the hexagonal ZrNiAl-type structure. Most of the previous works reported that both compounds have a valence fluctuation state. However, our results show that 4f electrons in CeRhSn have a localized nature whereas in CeRhIn, they show valence fluctuation. The elastic moduli and specific heat suggest that in CeRhSn, a crystal electric field plays a significant role in addition to a Kondo effect with Kondo temperature TK≈40 K. In CeRhIn, elastic, thermal, magnetic and transport properties can be understood by a renormalized two-band model with TK≥300 K.View full abstractDownload PDF (235K) -
Y. H. Matsuda, T. Inami, K. Ohwada, Y. Murata, H. Nojiri, Y. Murakami, ...2006 Volume 75 Issue 2 Pages 024710
Published: February 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSWe report the first high-field x-ray diffraction experiment using synchrotron x-rays and pulsed magnetic fields exceeding 30 T. The lattice deformation due to a magnetic-field-induced valence transition in YbInCu4 is studied. It has been found that the Bragg reflection profile at 32 K changes significantly at around 27 T due to the structural transition. In the vicinity of the transition field, the low field and high field phases alternate with the discontinuous change in the lattice constant. Thus, it is evident that the field-induced valence state transition is a first-order phase transition. The field dependence of the low-field-phase Bragg peak intensity is found to be roughly scaled with the magnetization.View full abstractDownload PDF (212K) -
Hiroshi Yamagami2006 Volume 75 Issue 2 Pages 024711
Published: February 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSFermi surface topology of transuranium compound NpGe3 is investigated from an itinerant 5f picture with a relativistic band calculation in a local-density approximation (LDA), thereby analyzing the frequency branches observed by the de Haas–van Alphen (dHvA) effect. The Fermi surface volume of NpGe3 is sensitive to the lattice constant because of its special shape. A LDA equilibrium lattice constant of NpGe3 is determined from total-energy minimization as a function of lattice constant under the AuCu3-type crystal structure. The Fermi surface obtained at the LDA equilibrium can explain precisely the origin of all the dHvA frequency branches like the familiar Fermi surface of Cu. This suggests that the fermiology of Np compounds should progress on the 5f band scheme, though Np-5f electrons are more localized than those of a lighter actinide atom.View full abstractDownload PDF (2707K) -
Eiichi Matsubara, Kuon Inoue, Eiichi Hanamura2006 Volume 75 Issue 2 Pages 024712
Published: February 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSRaman selection rules were observed to be violated dynamically under resonant and coherent pumping of the Raman-active two-phonon mode in the cubic perovskite-type oxide KTaO3. In this study, two intense femtosecond laser pulses having near infrared frequencies were used to excite the crystal with a relative time delay within ±200 fs. The frequency difference of the pulses was set to be almost equal to the frequency of one of the Raman-active two-phonon modes, with both phonons being at the Brillouin-zone (BZ) edge point. As a result, not only the conventional multistep coherent anti-Stokes Raman scattering (CARS) signals, but a new series of multistep signals with the frequency spacing of originally Raman-inactive single phonons were observed in the wavelength range from near infrared to the whole visible region. Importantly, the observed frequency spacing of the multistep signals does not correspond to the single-phonon frequency at the Γ-point but that at the BZ-edge point. In addition, the angle spacing of the observed signals is almost constant; it is also quite different from the angle distribution of the conventional CARS signals. A model mechanism of BZ folding from the BZ edge to the Γ-point due to coherent accumulation of two phonons at the BZ edge is presented to explain all aspects of this new phenomenon. Two phonons at the BZ edge and those at the Γ-point are anharmonically coupled within a decay time of coherent phonons, and those originally at the BZ edge become Raman-active. This novel phenomenon should provide a new tool to observe phonon modes at the BZ edge other than inelastic neutron scattering.View full abstractDownload PDF (685K) -
Kazunori Tanaka, Hiroaki Ikeda, Yunori Nisikawa, Kosaku Yamada2006 Volume 75 Issue 2 Pages 024713
Published: February 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSCeMIn5 (M=Co, Rh, Ir) are heavy fermion compounds with a HoCoGa5-type structure. CeCoIn5 and CeIrIn5 become superconducting at ambient pressure with Tc=2.3 and 0.4 K, respectively. On the other hand, CeRhIn5 is an antiferromagnet at ambient pressure, and becomes superconducting under pressures greater than 1.6 GPa. Nuclear-quadrupole-resonance (NQR), thermal conductivity, specific heat, and electrical resistivity measurements indicate that the superconductivity in CeMIn5 has line nodes. However, the pairing symmetry between dx2−y2 and dxy is controversial based on the angle-dependent measurements of thermal conductivity and specific heat under the magnetic field, respectively. Therefore, we investigate the gap structure of CeMIn5 by a detailed calculation. In order to reproduce the band structure characteristics of CeMIn5, we introduce a three-dimensional (3D) periodic Anderson model (PAM) and solve the Eliashberg equations. Thus, we identify the gap structure of CeMIn5 as the dx2−y2 symmetry. In addition, we discuss the pressure dependence of Tc and show that two opposing factors determine Tc. One factor is the momentum dependence of quasi-particle interaction and the other factor is the wave-function renormalization factor.View full abstractDownload PDF (262K) -
Makoto Nakamura, Yasuyuki Nakao, Victor T. Voronchev, Kotaro Hegi, Hid ...2006 Volume 75 Issue 2 Pages 024801
Published: February 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSIn D–T fusion plasma seeded with a small amount of 6Li, monochromatic 0.429-, 0.478- and 0.981-MeV γ rays are produced in the 6Li+D and 6Li+T nuclear reactions. In the present paper we investigate these processes in the appropriate plasma kinetic model. The non-Maxwellian tails of deuteron and triton distribution functions created due to nuclear elastic scattering of D–T α-particles by fuel ions are found to enhance crucially production of the diagnostic γ rays. This result can be considered as the first explicit demonstration that in a fusion plasma the role of suprathermal reaction channels induced by energetic knock-on ions can become comparable with (or even dominate) that of thermal ones. Possibilities of fuel ion and α-particle diagnostics using the reaction-produced γ rays are also discussed. It is pointed out for the first time that the behavior of α-particles during slowing-down could be diagnosed by detecting 0.981-MeV α-rays emitted in a nuclear reaction between knock-on tritons and 6Li admixture ions.View full abstractDownload PDF (524K) -
Takao Suzuki, Isao Watanabe, Akira Oosawa, Takao Fujiwara, Takayuki Go ...2006 Volume 75 Issue 2 Pages 025001
Published: February 15, 2006
Released on J-STAGE: August 27, 2009
JOURNAL RESTRICTED ACCESSDownload PDF (100K)
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