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Kosuke Morita, Kouji Morimoto, Daiya Kaji, Takahiro Akiyama, Sin-ichi ...
2004 Volume 73 Issue 10 Pages
2593-2596
Published: October 15, 2004
Released on J-STAGE: July 25, 2007
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The convincing candidate event of the isotope of the 113th element,
278113, and its daughter nuclei,
274111 and
270Mt, were observed, for the first time, in the
209Bi+
70Zn reaction at a beam energy of 349.0 MeV with a total dose of 1.7×10
19. Alpha decay energies and decay times of the candidates,
278113,
274111, and
270Mt, were (11.68±0.04 MeV, 0.344 ms), (11.15±0.07 MeV, 9.26 ms), and (10.03±0.07 MeV, 7.16 ms), respectively. The production cross section of the isotope was deduced to be 55
+150−45 fb (10
−39 cm
2).
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Akinori Hoshikawa, Takashi Kamiyama, Agus Purwanto, Kazuki Ohishi, Wat ...
2004 Volume 73 Issue 10 Pages
2597-2600
Published: October 15, 2004
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The magnetic structure of a chiral molecule-based magnet, [Cr(CN)
6][Mn(
S)-pnH(H
2O)](H
2O), has been studied using neutron powder diffraction as a function of temperature in the range from 4 K to 300 K. The 020 and 022 magnetic reflections were clearly observed below
Tc=38 K. On the basis of the intensity analysis of magnetic reflections, it was concluded that the magnetic structure is noncollinear ferrimagnetic with the magnetic (Shubnikov) space group
P2
12
1′2
1′, and magnetic moments of Cr and Mn atoms are mutually antiparallel along a direction near the
a-axis. Our findings imply that the long-period magnetic structure, if exists, is not a helical structure but a conical one.
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Makio Uwaha
2004 Volume 73 Issue 10 Pages
2601-2603
Published: October 15, 2004
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A simple reaction-type model that produces complete chiral symmetry breaking in crystallization is proposed. Crystals of homochirality are formed from achiral molecules. The model assumes i) perpetual mixing of the solution and abrasion of the crystals, ii) existence of chiral units smaller than the critical nucleus, iii) all processes have their counterparts, that is, decay of chiral units and crystals also occurs. We show that autocatalysis arises from the reaction of the chiral units so that chiral asymmetry is amplified as crystallization proceeds. Homochirality is achieved via slow relaxation in a later stage of crystallization.
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Yasuhiro Hatsugai
2004 Volume 73 Issue 10 Pages
2604-2607
Published: October 15, 2004
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We supply basic tools for the study of the topological order of a multiplet which is an eigenspace of a finite-dimensional normal operator with continuous parameters. We allow intrinsic degeneracies within the multiplet where a well-known standard procedure does not work. As an important example, we give novel expressions for a spin Hall conductance for unitary superconductors with equal spin pairing. Generic topological orders will be treated in this unified manner particularly with nontrivial topological degeneracies.
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Dai Aoki, Yoshiya Homma, Yoshinobu Shiokawa, Etsuji Yamamoto, Akio Nak ...
2004 Volume 73 Issue 10 Pages
2608-2611
Published: October 15, 2004
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We succeeded in observing de Haas–van Alphen (dHvA) oscillations in an antiferromagnet NpCoGa
5 with a tetragonal structure. The dHvA signal was significantly enhanced at higher fields than the metamagnetic transition field
Hm (=43 kOe for
H||[001]), where the antiferromagnetic state is changed into the field-induced ferromagnetic (paramagnetic) state. In the paramagnetic state, the Fermi surface was found to consist of two kinds of cylindrical main Fermi surface and small pocket Fermi surfaces. The cyclotron masses of the main Fermi surfaces were considerably large, ranging from 6 to 12
m0. This is the first case where the Fermi surface was determined experimentally in transuranium compounds.
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Kentaro Nomura, Daijiro Yoshioka
2004 Volume 73 Issue 10 Pages
2612-2615
Published: October 15, 2004
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Fractional quantum Hall states in bilayer systems at the total filling fraction ν=1⁄2 are examined numerically within some ranges of layer separation and interlayer tunneling. It is shown that the ground state changes continuously from a two-component state to a one-component state as the interlayer tunneling rate is increased, while the lowest excited state changes discontinuously. This fact explains the unusual behavior of the observed activation energies which reveals an upward cusp as a function of interlayer tunneling. Some trial wave functions for the ground state and quasihole excited states are inspected.
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Kazuya Yamamoto, Munetaka Taguchi, Nozomu Kamakura, Koji Horiba, Yasut ...
2004 Volume 73 Issue 10 Pages
2616-2619
Published: October 15, 2004
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We investigate the temperature-induced mixed valence transition in EuNi
2(Si
0.20Ge
0.80)
2 using Hard X-ray (5940 eV) photoemission spectroscopy (HX-PES), with a probing depth larger than 5 nm. The Eu 3
d, Ni 2
p and Ge 2
p core-level states are studied below and above the critical valence transition temperature,
Tv=80 K. HX-PES spectra at 40 K and 120 K show the mixed valence transition, with clear changes in the divalent and trivalent Eu 3
d chemically shifted features, and negligible changes in the Ni 2
p and Ge 2
p states. The Eu 3
d spectral shapes match very well with the results of the atomic calculations of the Eu
2+ and Eu
3+ configurations, confirming intra-atomic multiplet features. The Eu 3
d HX-PES spectra indicate a mean valence of 2.70±0.03 at 40 K which changes to 2.40±0.03 at 120 K, in good accord with the results of bulk Eu L-edge X-ray absorption spectroscopy measurements.
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Hironori Nakao, Masami Tsubota, Fumitoshi Iga, Kazuyuki Uchihira, Tosh ...
2004 Volume 73 Issue 10 Pages
2620-2623
Published: October 15, 2004
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Orbitally ordered states of a Ti
t2g-electron in Y
1−xCa
xTiO
3 (0<
x≤0.5) have been systematically investigated by the resonant X-ray scattering (RXS) technique near the Ti
K-edge. The RXS intensities at 1
s→3
d transition energy (pre-edge) reflecting the 3
d-orbital ordering markedly decrease with increasing Ca concentration toward the ferromagnetic–paramagnetic phase boundary (
xFP∼0.15). The intensity remaining above
xFP decreases gradually and almost disappears at the metal–insulator transition (
xMI∼0.4). Namely, it is suggested that the orbital ordering is strongly suppressed toward
xFP, and vanishes at
xMI. The Ca concentration dependence of the Jahn–Teller distortion determined by X-ray structural analysis is consistent with the orbital state obtained by the RXS experiment.
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Masaru Onoda, Gen Tatara, Naoto Nagaosa
2004 Volume 73 Issue 10 Pages
2624-2627
Published: October 15, 2004
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We study the anomalous Hall effect (AHE) for the double exchange model with the exchange coupling |
JH| being smaller than the bandwidth |
t| for the purpose of clarifying the following unresolved and confusing issues: (i) the effect of the underlying lattice structure, (ii) the relation between AHE and the skyrmion number, (iii) the duality between real and momentum spaces, and (iv) the role of disorder scatterings; which is more essential, σ
H (Hall conductivity) or ρ
H (Hall resistivity)? Starting from a generic expression for σ
H, we resolve all these issues and classify the regimes in the parameter space of
JHτ (τ: elastic scattering time) and λ
s (length scale of spin texture). There are two distinct mechanisms of AHE; one is characterized by the real-space skyrmion number and the other by the momentum-space skyrmion density at the Fermi level, which occur in different regimes of the parameter space.
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Muneyuki Tsuda, Wilson Agerico Diño, Hiroshi Nakanishi, Hideaki ...
2004 Volume 73 Issue 10 Pages
2628-2630
Published: October 15, 2004
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In the present study, we investigate H
2 desorption from a magnesium hydride MgH
2 cluster by performing total energy calculations based on the density functional theory (DFT). We calculate the potential energy surface (PES) for the H
2 desorption from a (MgH
2)
5 cluster. According to the total atomic charges of the Mg and H atoms at the initial (MgH
2)
5 cluster, the Mg–H bond is ionic-like. Because of this, the activation barrier for the H
2 desorption is considerably high (3.30 eV). Moreover, the structural relaxation for the system, allowing for only the two Mg atoms closest to the two desorbing H atoms, does not largely affect the potential energy of the system. The results indicate that the ionic-like Mg–H interaction is related to the thermodynamical stability of MgH
2.
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Sogo Kuroiwa, Hiroyuki Takagiwa, Maki Yamazawa, Jun Akimitsu, Kazuki O ...
2004 Volume 73 Issue 10 Pages
2631-2634
Published: October 15, 2004
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The temperature (
T) and magnetic field (
H) dependences of the magnetic penetration depth, λ(
T,
H), in Ca(Al
0.5Si
0.5)
2 exhibits a significant deviation from that expected for conventional BCS superconductors. In particular, it is inferred from the field dependence of λ(
H) (∝
H) at 2.0 K that the quasiparticle excitation is strongly enhanced by the Doppler shift. This suggests that the superconducting order parameter in Ca(Al
0.5Si
0.5)
2 is characterized by a small energy scale, Δ
S⁄
kB\\simeq2 K, originating either from the anisotropy or two-gap structure.
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Hiroshi Shimahara
2004 Volume 73 Issue 10 Pages
2635-2638
Published: October 15, 2004
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Antiferromagnetic superconductors in a magnetic field are studied. We examine a mechanism which significantly reduces the Pauli paramagnetic pair-breaking effect. The mechanism is realized even in the presence of the orbital pair-breaking effect. We illustrate it using a three-dimensional model with an intercalated magnetic subsystem. The upper critical field is calculated for various parameters. It is shown that the upper critical field can reach several times the pure Pauli paramagnetic limit. The possible relevance to the large upper critical field observed in the heavy fermion antiferromagnetic superconductor CePt
3Si discovered recently is briefly discussed. We try to understand the large upper critical field in the compound CePt
3Si and field-induced superconductivity in the compound CePb
3 within a unified framework.
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Ritsuya Tomita, Hiroko Koga, Tetsuji Uchiyama, Ienari Iguchi
2004 Volume 73 Issue 10 Pages
2639-2641
Published: October 15, 2004
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The synthesis of a novel silver boron intermetallic compound (nominal composition: AgB
2) and the occurrence of superconductivity are reported. The samples are prepared by a thin-film pulsed laser deposition method incorporating a cap technique and an annealing process in a high vacuum. A sharp transition to zero resistance at
Tc=6.7 K is observed. The observed
Tc is significantly lower than the theoretically predicted
Tc of AgB
2 diboride.
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Yosuke Shindo, Hidekazu Tanaka
2004 Volume 73 Issue 10 Pages
2642-2645
Published: October 15, 2004
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The effect of exchange randomness on field-induced magnetic ordering was investigated through specific heat measurements in Tl
1−xK
xCuCl
3 with
x≤0.22. The isostructural parent compounds TlCuCl
3 and KCuCl
3 are coupled spin dimer systems with a gapped ground state and their field-induced antiferromagnetic ordering is described by the Bose–Einstein condensation (BEC) of spin triplets. Well-defined field-induced phase transitions were observed in Tl
1−xK
xCuCl
3. The critical exponent φ of the phase boundary defined by
T(
H)∝(
H−
Hc)
1⁄φ is reevaluated in TlCuCl
3 as φ=1.67±0.07, which is close to φ
BEC=3⁄2 derived from the magnon BEC theory. For
x≠0, the exponent φ decreases systematically with
x. The phase boundary observed below 2 K for
x>0.1 approximates a linear function of temperature
T. In the low-field region for
H<
Hc, no magnetic ordering is observed despite finite susceptibility. These properties are discussed in connection with the Bose glass phase argued by Fisher
et al. [Phys. Rev. B
40 (1989) 546].
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Taeko Semba, Takahiro Fukui
2004 Volume 73 Issue 10 Pages
2646-2649
Published: October 15, 2004
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We study the spin-wave dispersion of localized spins in a disordered double-exchange model using the perturbation theory with respect to the strength of the disorder potential. We calculate the dispersion up to the next-leading order, and extensively examine the case of one dimension. We show that in that case, disorder yields anomalous gap-like behavior at the Fermi wave number of the conduction electrons.
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Yasuo Narumi, Koichi Katsumata, Yoshikazu Tabata, Shojiro Kimura, Yosh ...
2004 Volume 73 Issue 10 Pages
2650-2653
Published: October 15, 2004
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Synchrotron X-ray diffraction measurements on a spin–Peierls material CuGeO
3 in applied magnetic fields,
H, up to 15 T are made. We find that the temperature,
T, dependence of the incommensurate Bragg peak at a lower
H is quite different from that at a higher
H. At sufficiently high fields, we find that the lattice incommensurability, δ
l, is almost independent of
T, while at
H slightly above the critical field = 12.25 T for the commensurate to incommensurate transition, δ
l decreases with increasing
T. We interpret that this finding is due to a stabilization of the incommensurate state by a strong magnetic field which suppresses thermal fluctuations.
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Kazuaki Narita
2004 Volume 73 Issue 10 Pages
2655-2661
Published: October 15, 2004
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As an extension of the result in the preceding paper [J. Phys. Soc. Jpn.
72 (2003) 1339], we propose a group of partial differential equations and their discrete models with the following two properties. (1) Lorentz invariance (exact or approximate). (2) Ability of exhibiting elliptic function solutions. We present particular solutions to these equations, including an N-kink solution as a special case.
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Partha Guha
2004 Volume 73 Issue 10 Pages
2662-2666
Published: October 15, 2004
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The Lie algebra of pseudodifferential symbols Ψ
D(
S1) on
S1 has a natural Lie–Poisson structure. The Moyal deformation of dispersionless Korteweg–de Vries (KdV) equation is constructed from the action of \\mathop
Vect(
S1) on Ψ
D(
S1). We also study the Moyal deformation of supersymmetric two-boson KdV equation. We offer their Lax representations. Using Souriau–Kravchenko–Khesin cocycle we are able to construct KdV equation.
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Akira Nakamura
2004 Volume 73 Issue 10 Pages
2667-2679
Published: October 15, 2004
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We present the (1+1 dimensional) discrete version of the generalized ladder operator method of the special functions. It is shown that this scheme can give the
N-soliton solutions of the discrete cylindrical Toda equation and the quotient-difference equation.
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Hiroki Tutu, Naoya Fujiwara
2004 Volume 73 Issue 10 Pages
2680-2696
Published: October 15, 2004
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We propose a systematic perturbation expansion method for getting phase diagrams on dynamical symmetry breaking which is caused by varying the amplitude
h or frequency Ω of the periodic external force
hcos(Ω
t) in systems under the Landau type potentials. The method is based on the Fourier expansion and the Floquet theorem. We formulate the method by utilizing an introductory example, bistable system driven by the periodic external force. An order estimation criterion based on the magnitude of the Fourier coefficient for the fundamental frequency Ω plays an essential role in order to construct the systematic expansion method. According to the criterion, analytical expressions for the transition point and weak nonlinear expansions (Landau type expansions) near the transition point are derived in desired orders of approximation. We also show two applications of the method: the dynamical symmetry breaking in the XY-spin system with uniaxial anisotropy and tristable system at the presence of the forcing. The method predicts all behaviors of phase diagrams on those. The latter example may be the first legitimate treatment of subcritical pitchfork bifurcation in the frameworks of the dynamic phase transition.
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Yasuaki Kobayashi, Masaki Sano
2004 Volume 73 Issue 10 Pages
2697-2700
Published: October 15, 2004
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We numerically investigate the nonequilibrium steady state of a one-dimensional rarefied granular system in which each particle is driven by Gaussian white noise and subject to inelastic mutual collisions. We find that the dynamic structure factor
S(
q,
t) decays as exp(−
Dq2t2), which is in marked contrast to the usual Fickian behavior exp(−
Dq2t). Employing newly obtained
S(
q,
t), we demonstrate that the static spatial correlation function and the one-point time correlation function obey the same scaling behavior.
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Hidetoshi Nishimori, Peter Sollich
2004 Volume 73 Issue 10 Pages
2701-2707
Published: October 15, 2004
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Upper and lower bounds are given for the number of equivalence classes of error patterns in the toric code for quantum memory. The results are used to derive a lower bound on the ground-state energy of the ±
J Ising spin glass model on the square lattice with symmetric and asymmetric bond distributions. This is a highly non-trivial example in which insights from quantum information lead directly to an explicit result on a physical quantity in the statistical mechanics of disordered systems.
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Kazuyuki Nakayama, Shigeki Furue, Tomoji Ogawa, Masatoshi Misono, Taka ...
2004 Volume 73 Issue 10 Pages
2708-2711
Published: October 15, 2004
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A high-resolution coherent spectroscopy, based on the iterative excitation using the atomic response, is studied. The Zeeman quantum beats in the ground state 3
2S1⁄2 of Na atoms were produced and monitored by optical means. Significant reductions of the spectral width were observed for resonance lines broadened by inhomogeneity of the magnetic field. Theoretical analysis for the coherence-beat signals is given. The experimental results were well explained by the theory.
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Shigeyuki Aono
2004 Volume 73 Issue 10 Pages
2712-2717
Published: October 15, 2004
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The theory distinguishing the molecular chirality in the optical transition is presented. The characteristic combination responsible for this transition is the angular momentum of molecule and the magnetic field produced by photons. The amplitude is so small estimated
v⁄
c times that of the dipole transition. The specified model employed is a triangle with unequal sides which plays an enantio-surface of the chiral molecule.
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Radostin Danev, Kuniaki Nagayama
2004 Volume 73 Issue 10 Pages
2718-2724
Published: October 15, 2004
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An extension of the Complex Observation series based on a novel imaging mode of the transmission electron microscope (TEM) is presented. A half plane phase plate is used to produce images that exhibit topographic-like appearances and have spectral modulation similar to the modulation of Zernike phase contrast TEM (ZPC-TEM) images. The Differential Interference Contrast (DIC) technique in light microscopy produces a similar contrast. The main difference between the two techniques is the asymmetry in one direction of the spectral modulation of the half plane phase plate images, which causes the topographic-like appearance of these images. The complex form of the object wave can be numerically rebuilt using a properly demodulated half plane phase plate image and a conventional TEM image. Experimental results demonstrating the success of the complex reconstruction scheme are presented.
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Kuniaki Nagayama
2004 Volume 73 Issue 10 Pages
2725-2731
Published: October 15, 2004
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Conventional phase retrieval in transmission microscopy is applicable only to weak objects that perturb the incidence with a phase that is π⁄2 or smaller. We propose a novel phase retrieval technique applicable to strong objects. The innovation core is the scanning of a knife-edge, which is conventionally fixed to recover phase information. The synchronous operation between the scanning of the knife-edge and the image accumulation enables a novel spatial filter, which draws phase retardations by objects in the form of their first derivative. Combining the left- and right-scanning of the knife-edge can completely expel image components that are non-linear to the wavefront functions. Theoretical formulation of knife-edge scanning filters and corresponding numerical simulations specific to an electron microscope are proposed.
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Takao Itami, Kiyosi Horiuti
2004 Volume 73 Issue 10 Pages
2732-2738
Published: October 15, 2004
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In the present work we carried out the assessment of the generalized scale-similarity model (
CB−
CS) in compressible homogeneous isotropic turbulence at moderately high Reynolds numbers, by comparing with previous dynamic subgrid-scale (SGS) stress models. In an
a priori test, it was shown that the SGS stress estimated using the
CB−
CS model had the closest agreement with the exact value, and the energy transfer between subgrid-scale energy and grid-scale energy was most accurately predicted using the
CB−
CS model. In an actual large-eddy simulation, it was shown that both the development of turbulent energy and the evolution of the turbulent structure, such as the vortex tube, predicted using the
CB−
CS model were close to those of the filtered DNS data. The primary cause for a high accuracy of the scale-similarity model was explored.
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Masato Makino, Masao Doi
2004 Volume 73 Issue 10 Pages
2739-2745
Published: October 15, 2004
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We give a general formulation of handling the Brownian motion of a rigid particle of arbitrary shape in a Newtonian fluid subject to external force, torque and velocity field. We show how to include the effect of the Brownian motion. As an example, we discuss the effect of the translation–rotation coupling on the Brownian motion of free particle.
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Ryuichi Goto, Fuyuki Shimojo, Shuji Munejiri, Kozo Hoshino
2004 Volume 73 Issue 10 Pages
2746-2752
Published: October 15, 2004
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The structural and electronic properties of liquid Ge–Sn alloys are investigated by
ab initio molecular-dynamics simulations. The calculated total static structure factors of liquid Ge
0.8Sn
0.2 alloys at 1273, 1523 and 1773 K are in good agreement with the recent experimental results obtained by the neutron scattering and their temperature dependence is very weak; with increasing temperature, the peak heights of the total structure factors and the partial radial distribution functions become slightly lower though their positions remain almost same. The long-wavelength limit of the concentration–concentration structure factor increases with decreasing temperature, which is consistent with the phase-separating tendency. The self-diffusion coefficients for Ge and Sn atoms in liquid Ge
0.8Sn
0.2 alloys are obtained from the calculated velocity autocorrelation functions and the mean square displacements and are compared with those values calculated by
ab initio molecular-dynamics simulation for pure liquid Ge and Sn, respectively. The total and partial electronic densities of states obtained by our simulation do not depend on the temperature and show that the liquid alloys considered in this paper are metallic, though the coexistence of the covalent-like and ‘metallic’ bonds is shown by the analyses of the maximally localized Wannier functions.
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Hiromitsu Matsuda, Tomonori Koda, Akihiro Nishioka, Susumu Ikeda
2004 Volume 73 Issue 10 Pages
2753-2758
Published: October 15, 2004
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We study isotropic–nematic (Iso–N) phase transition in mixtures of hard rods of different lengths
LA and
LB in an external field by using the symmetry breaking potential method with the mean field approximation. We discuss effect of the external field on a triple point and phase co-existence regions. Iso+N+N triple point, which appears on phase diagram in the pressure–composition plane for mixtures showing N+N co-existence, is moved to shorter rod side on the phase diagram by the external field. We find for the case of
LA⁄
LB=4 that, depending on pressure, three types appear for phase diagrams in the external field-composition plane. One type shows Iso+N co-existence region that has upper critical solution field, another shows Iso+N and N+N co-existence region critical solution field of which is higher than critical field of monodisperse shorter rods, and the other shows Iso+N+N triple point.
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Hasafumi Hanawa, Yutaka Moritomo, Junichiro Tateishi, Yasuo Ohishi, Ke ...
2004 Volume 73 Issue 10 Pages
2759-2762
Published: October 15, 2004
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Hydrostatic pressure effects on the structural and magnetic properties were investigated for two potassium–cobalt-iron hexacyanides, K
0.12Co[Fe(CN)
6]
0.70·4.87H
2O (high [Fe(CN)
6] vacancy concentration
v) and K
0.36Co[Fe(CN)
6]
0.82·4.56H
2O (low-
v). In both the compounds, we observed a pressure-induced volume transition at 300 K from the large volume (LV) phase to the small volume (SV) phase. In the high-
v compound, the magnitude of the effective moment μ
eff gradually decreases with pressure increases. We ascribed it to the gradual spin state transformation of Co
3+ from the high-spin state (
S=2) to the low-spin state (
S=0).
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Teruaki Yanagisawa, Takashi Itoh, Yasuo Saruyama, Susumu Fujiwara
2004 Volume 73 Issue 10 Pages
2763-2767
Published: October 15, 2004
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Three types of amorphous phases (ferroelectric metastable phase A with large remanent polarization, ferroelectric metastable phase B with small remanent polarization and paraelectric stable phase C) are identified in as-quenched and/or annealed nylon 6 films on the basis of the thermal data obtained by light-modulated differential scanning calorimetry (LMDSC) as well as X-ray data, which show different glass transition temperatures and
d-spacings. The irreversible exothermic anomaly at 328 K observed through heating process in the conventional DSC is attributed to transition from phases A and/or B to nematic phase. The transition from phase A to phase B is considered to complete after 15 min annealing at 320 K on the basis of the LMDSC data, which corresponds to abrupt diminution of the remanent polarization by the correspondent annealing condition. Such results suggest that ferroelectricity of nylon 6 film is mainly attributed to phase A (frozen state of the melt) formed in the quenched nylon 6 thin film.
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Jobu Matsuno, Makoto Seto, Shinji Kitao, Yasuhiro Kobayashi, Rie Haruk ...
2004 Volume 73 Issue 10 Pages
2768-2770
Published: October 15, 2004
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Iron perovskites CaFeO
3 and La
0.33Sr
0.67FeO
3 show charge disproportionation, resulting in charge-ordered states with “Fe
3+”:“Fe
5+”=1:1 and =2:1, respectively. We have performed nuclear resonant scattering measurements of phonon density of states in CaFeO
3 and La
0.33Sr
0.67FeO
3. With decreasing temperature, we found changes in the phonon density of states in the region of 30–60 meV in CaFeO
3, while only a small change was observed in La
0.33Sr
0.67FeO
3. This finding gives support to the previous finding that the charge disproportionation is driven by electron–phonon interaction in CaFeO
3, and electronically in La
0.33Sr
0.67FeO
3.
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Haruka Sugimoto, Tamio Oguchi
2004 Volume 73 Issue 10 Pages
2771-2776
Published: October 15, 2004
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Structural parameters of β-ZrNCl with SmSI and YOF types are determined by first-principles total-energy and atomic-force calculations. Obtained structural parameters for SmSI-type ZrNCl are in good agreement with the experimental ones. Differences between the optimized parameters for YOF-type ZrNCl and experimental ones for YOF-type Li
0.16ZrNCl show significant Li-doping effects on distances of the nearest N–N and Zr–Cl atoms and flatness of double Zr–N layers. Electronic band structures for the optimized crystal structure as well as the observed one are compared and discussed in conjunction to the structural difference. A
1g phonon modes are evaluated from the force constants calculated and found to be rather insensitive to structural type and Li doping.
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Shutaro Chiba, Yoshiyuki Ono
2004 Volume 73 Issue 10 Pages
2777-2780
Published: October 15, 2004
Released on J-STAGE: July 25, 2007
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The periodic lattice distortion BOW owing to the electron–lattice interaction and the spin density wave SDW owing to the electron–electron interaction in the two-dimensional Peierls–Hubbard model having a half-filled electronic band are studied numerically within the Hartree–Fock approximation. It is shown that the phase transition from the BOW to the SDW behaves as the first order phase transition when the on-site electron–electron interaction
U is increased continuously. There is no region of
U where the BOW and the SDW coexist as a uniform phase.
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Takeshi Suwa, Kazuo Takayanagi, Enrico Lipparini
2004 Volume 73 Issue 10 Pages
2781-2789
Published: October 15, 2004
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Multiple scattering processes in two-dimensional electron systems with an arbitrary spin polarization are expressed as a spin-dependent effective interaction operator, which allows applications in various two-dimensional electron systems. Effects of the spin polarization on the correlation energy and the pair correlation function are discussed in detail in connection with the polarization-dependence of the effective interaction.
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Masaki Murase, Aya Tobo, Hideya Onodera, Yukiko Hirano, Tadaaki Hosaka ...
2004 Volume 73 Issue 10 Pages
2790-2794
Published: October 15, 2004
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Anomalous temperature dependence of electrical resistivity was found to be ubiquitous among the compounds RNiC
2 with R = La, Ce, Nd, Sm, Gd, Tb and Er. Lattice parameters were also observed to exhibit anomalous temperature dependence for some of the compounds studied by X-ray diffraction. It is argued that the existence of charge modulated structures is the cause of the former anomalies. The latter anomalies, on the other hand, are likely to be related to the coupling between the lattice and the f-electrons. Results of heat capacity measurements are used to estimate crystal field levels in NdNiC
2 and SmNiC
2.
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Yoichi Tanaka, Norio Kawakami
2004 Volume 73 Issue 10 Pages
2795-2801
Published: October 15, 2004
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We investigate spin-polarized transport phenomena through double quantum dots coupled to ferromagnetic leads in series. By means of the slave-boson mean-field approximation, we calculate the conductance in the Kondo regime for two different configurations of the leads: spin-polarization of two ferromagnetic leads is parallel or anti-parallel. It is found that transport shows some remarkable properties depending on the tunneling strength between two dots. These properties are explained in terms of the Kondo resonances in the local density of states.
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Masao Nakamura, Makoto Izumi, Naoki Ogawa, Hiroyuki Ohsumi, Yusuke Wak ...
2004 Volume 73 Issue 10 Pages
2802-2806
Published: October 15, 2004
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We investigated the origin of the energy splitting observed in the resonant x-ray scattering (RXS) in manganites. Using thin film samples with controlled lattice parameters and orbital states at a fixed orbital filling, we estimated that the contribution of the interatomic Coulomb interaction relative to the Jahn–Teller mechanism is insignificant and at most 0.27. This indicates that RXS probes mainly Jahn–Teller distortion in manganites.
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S. Okuma, M. Kamada
2004 Volume 73 Issue 10 Pages
2807-2812
Published: October 15, 2004
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We have measured current (
I)-induced voltage (
V) noise
SV of thick and thin amorphous Mo
xSi
1−x films with different transition temperatures
Tc, but with similar critical current densities, to study vortex dynamics driven by
I at zero field below
Tc. Origin of noise is due to density fluctuations of thermally created free vortices and antivortices in the presence of
I. With increasing temperature
T,
SV⁄
V shows a decrease and tends to zero near
Tc, where
SV⁄
V for the thick and thin films follows the single scaling functions expressed as
SV⁄
V=
A(1−
T⁄
Tc)
n (
n≈5–6) with large and small values of
A, respectively. This means that the physical mechanism responsible for the
T dependence of noise (or vortex-density fluctuations) for the thick and thin films is qualitatively similar, but quantitatively dominated by the dimensionality.
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N. Ishikawa, C. J. van der Beek, A. Dunlop, G. Jaskierowicz, Ming Li, ...
2004 Volume 73 Issue 10 Pages
2813-2821
Published: October 15, 2004
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Using 30 MeV C
60 fullerene irradiation, we have produced latent tracks of diameter 20 nm and length 200 nm, near the surface of single crystalline Bi
2Sr
2CaCu
2O
8+δ. A preliminary transmission electron microscopy study shows evidence for a very high density of deposited energy, and the ejection of material from the track core in very thin specimens. The latent tracks reveal themselves to be exceptionally strong pinning centers for vortices in the superconducting mixed state. Both the critical current density and magnetic irreversibility line are significantly enhanced. The irradiated crystals present salient features of the (
B,
T) phase diagram of vortex matter
both of pristine crystals, such as the first order vortex phase transition,
and the exponential Bose-glass line characteristic of heavy ion-irradiated crystals. We show that the latter is manifestly independent of the pinning potential.
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Sotaro Sasaki, Hiroaki Ikeda, Kosaku Yamada
2004 Volume 73 Issue 10 Pages
2822-2828
Published: October 15, 2004
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We investigate pairing symmetry and transition temperature in the trellis-lattice Hubbard model. We solve the Éliashberg equation using the third-order perturbation theory with respect to the on-site repulsion
U. We find that a spin-singlet state is very stable in a wide range of parameters. On the other hand, when the electron number density is shifted from the half-filled state and the band gap between two bands is small, a spin-triplet superconductivity is expected. Finally, we discuss a possibility of unconventional superconductivity and pairing symmetry in Sr
14−xCa
xCu
24O
41.
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Osamu Sakai, Yatramohan Jana, Ryuji Higashinaka, Hideto Fukazawa, Sato ...
2004 Volume 73 Issue 10 Pages
2829-2833
Published: October 15, 2004
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We have synthesized new compounds
R2Nb
2O
7 (
R=Dy, Yb) based on the pyrochlore structure. Both are insulating at room temperature. Susceptibility measurements reveal that Dy
2Nb
2O
7 exhibits a spin freezing around 1 K without any long range ordering down to 0.3 K, while the Yb-based compound does not show any ordering down to 0.3 K. Specific heat measurements show that both compounds have a well-isolated doublet ground state. Magnetization and magnetic contribution to the specific heat for both systems solely come from rare earth ions, which suggests that the Nb site network has nonmagnetic state as reported for Y
2Nb
2O
7.
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Toshihiro Usa, Kazuya Kamazawa, Hirofumi Sekiya, Shin Nakamura, Yorihi ...
2004 Volume 73 Issue 10 Pages
2834-2840
Published: October 15, 2004
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Magnetic properties of ZnFe
2O
4 were studied for various specimens prepared by different thermal and artificial treatments using neutron scattering, Mössbauer spectroscopy and DC and AC susceptibilities. We found a strong correlation between the magnetic Bragg peak intensity and the Mössbauer absorption line-width. Comparing with the susceptibility data, it is discussed what are the intrinsic magnetic properties of ZnFe
2O
4 as a typical 3-D geometrical spin frustration system.
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Yoichi Nishiwaki, Tetsuya Kato, Yasuaki Oohara, Katsunori Iio
2004 Volume 73 Issue 10 Pages
2841-2844
Published: October 15, 2004
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A single-crystal neutron diffraction study was made on the structural and magnetic phase transitions of the distorted-triangular-lattice Ising-like antiferromagnet RbCoBr
3. Below the structural phase transition point,
Tst1=90 K, the chemical unit cell was found to be enlarged to (\\sqrt3
a,\\sqrt3
a,
c). The temperature dependence of the (1,1,1) magnetic Bragg peak of this crystal shows absence of the intermediate ‘partial disorder’ phase, which is known to appear between the paramagnetic and ferrimagnetic phases of the typical Ising-like triangular-lattice antiferromagnets CsCoCl
3 and CsCoBr
3. The present result, that the partial disorder phase vanishes, is due to the release of spin frustration.
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Ryuji Higashinaka, Hideto Fukazawa, Kazuhiko Deguchi, Yoshiteru Maeno
2004 Volume 73 Issue 10 Pages
2845-2850
Published: October 15, 2004
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We report the specific heat of single crystals of the spin ice compound Dy
2Ti
2O
7 at temperatures down to 100 mK in the so-called Kagome ice state. In our previous paper, we showed the anisotropic release of residual entropy in different magnetic field directions and reported new residual entropy associated with spin frustration in the Kagome slab for field in the [111] direction. In this paper, we confirm the first-order phase transition line in the field–temperature phase diagram and the presence of a critical point at (0.98 T, 400 mK), previously reported from the magnetization and specific-heat data. We newly found another peak in the specific heat at 1.25 T below 0.3 K. One possible explanation for the state between 1 T and 1.25 T is the coexistence of states with different spin configurations including the 2-in 2-out state (Kagome ice state), the 1-in 3-out state (ordered state) and paramagnetic state (free-spin state).
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Hidekazu Aoki, Toshiro Sakakibara, Kazuyuki Matsuhira, Zenji Hiroi
2004 Volume 73 Issue 10 Pages
2851-2856
Published: October 15, 2004
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Field variation of the entropy
S(
H) of the spin ice compound Dy
2Ti
2O
7 has been examined by means of magnetocaloric effect measurements in a magnetic field
H||[111], with attention focused on the ice-rule breaking spin-flip transition. At
T=0.35 K,
S(
H) exhibits a plateau in the kagomé ice state up to ∼0.8 T, followed by a sharp decrease at 0.9 T where a first-order transition to the saturated state occurs. Slightly above the critical point of the transition (
Tcr\\simeq0.36 K),
S(
H) at 0.4 K and 0.5 K exhibits a pronounced peak at the spin flip field of ∼0.9 T indicating an enhanced degeneracy due to coexistence of “two-in, two-out” and “three-in, one-out” states at the field. The peak height of
S(
H) is, however, strongly temperature dependent and substantially smaller than that expected from a nearest-neighbor spin ice model, suggesting the presence of certain magnetic correlation in the system.
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Minoru Soda, Yukio Yasui, Masafumi Ito, Satoshi Iikubo, Masatoshi Sato ...
2004 Volume 73 Issue 10 Pages
2857-2862
Published: October 15, 2004
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Neutron diffraction studies have been carried out on a single crystal of oxygen-deficient perovskite NdBaCo
2O
5.5 in the temperature (
T) range between 7 K and 320 K. We have found a magnetic transition at
Tc∼170 K, and a rapid change of the intensities of several reflections at
T*∼30 K. The magnetic structures have been analyzed at 7 K (<
T*) and 40 K (
T*<
T<
Tc). Non-collinear magnetic structures, which are based on the G-type antiferromagnetic structure, are proposed at these temperatures. In the
T region between
T* and
Tc, Co
3+ ions of CoO
6 octahedra are in the intermediate spin state, and those of CoO
5 pyramids are in the high spin state. In the region of
T<
T*, the magnitude of the Co
3+ spins in the octahedra decreases gradually as
T decreases, suggesting that the spin state approaches the low spin state. It is pointed out that the spin state of Co ions depends on the local structure around them.
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Ae Ran Lim, Tae-Gab Jang, Jin-Hae Chang, Se-Young Jeong
2004 Volume 73 Issue 10 Pages
2863-2867
Published: October 15, 2004
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The temperature dependences of the stress–strain hysteresis and of the optical polarizing microscopy results in the K
3H(SO
4)
2 single crystal grown by using the slow evaporation method were measured. From these, it was determined that the K
3H(SO
4)
2 single crystal underwent a ferroelastic phase transition near
Tc=481 K. Also, we studied the ferroelastic domain switching due to external stress in K
3H(SO
4)
2 single crystals. The ferroelastic domain switching stress due to the saturation effect was about 0.3 MPa. This means that when an external stress of 0.3 MPa is applied to K
3H(SO
4)
2 crystals, a transformation occurs from the twin-domain state to the single-domain state. This crystal easily transforms to a single domain under the influence of a slight external stress. In addition, the spin–lattice relaxation rates for
1H and
39K nuclei in K
3H(SO
4)
2 single crystals were determined as a function of temperature. The spin–lattice relaxation of
1H cannot be represented by the Bloembergen–Purcell–Pound (BPP) function, so is not related to HSO
4 motion. The recovery traces of
39K, which predominantly undergoes quadrupole relaxation, can be represented by a linear combination of two exponential functions. The temperature dependences of the relaxation rates for
39K can be described with a simple power law
T1−1=
AT2. The spin–lattice relaxation rates for the
39K nucleus in K
3H(SO
4)
2 crystals are in accordance with a Raman process dominated by a phonon mechanism.
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Kenji Yonemitsu
2004 Volume 73 Issue 10 Pages
2868-2878
Published: October 15, 2004
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Photoinduced dynamics of charge density and lattice displacements is calculated by solving the time-dependent Schrödinger equation for a one-dimensional extended Peierls–Hubbard model with alternating potentials for the mixed-stack organic charge–transfer complex, TTF–CA. A pulse of oscillating electric field is incorporated into the Peierls phase of the transfer integral. The frequency, the amplitude, and the duration of the pulse are varied to study the nonlinear and cooperative character of the photoinduced transition. When the dimerized ionic phase is photoexcited, the threshold behavior is clearly observed by plotting the final ionicity as a function of the increment of the total energy. Above the threshold photoexcitation, the electronic state reaches the neutral one with equidistant molecules after the electric field is turned off. The transition is initiated by nucleation of a metastable neutral domain, for which an electric field with frequency below the linear absorption peak is more effective than that at the peak. When the pulse is strong and short, the charge transfer takes place on the same time scale with the disappearance of dimerization. As the pulse becomes weak and long, the dimerization-induced polarization is disordered to restore the inversion symmetry on average before the charge transfer takes place to bring the system neutral. Thus, a paraelectric ionic phase is transiently realized by a weak electric field. It is shown that infrared light also induces the ionic-to-neutral transition, which is characterized by the threshold behavior.
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