Journal of the Physical Society of Japan
Online ISSN : 1347-4073
Print ISSN : 0031-9015
ISSN-L : 0031-9015
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Volume 66, Issue 11
Displaying 51-65 of 65 articles from this issue
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  • Pair Dynamical Correlated-Effective-Field Approximation
    Satoshi Kokado, Naoshi Suzuki
    Subject area: Magnetic properties and materials.
    1997 Volume 66 Issue 11 Pages 3605-3610
    Published: November 01, 1997
    Released on J-STAGE: October 01, 1999
    DOIhttps://doi.org/10.1143/jpsj.66.3605
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    The dynamical correlated-effective-field approximation (DCEFA) developed by Suzuki is extended to the pair-approximation, in which the spin-pair is solved exactly and the interaction between the pairs is treated by the DCEFA. The approximation is applied to calculate magnetic excitation and uniform static susceptibility of S=1/2 exchange-alternating chains.The obtained results agree reasonably well with those obtained by the exact diagonalization method for finite spins. The approximation is applied also to real pseudo-one-dimensional antiferromagnetic-ferromagnetic alternating systems such as Cu(TIM)CuCl4, (4-BzpipdH)CuCl3 and MeNN, and the exchange couplings including interchain coupling in these systems are evaluated.
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  • Spin-Wave Theory of Magnetic Ordering in UNi4B
    Syougo Tejima, Akihide Oguchi
    Subject area: Magnetic properties and materials.
    1997 Volume 66 Issue 11 Pages 3611-3616
    Published: November 01, 1997
    Released on J-STAGE: October 01, 1999
    DOIhttps://doi.org/10.1143/jpsj.66.3611
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    We study properties of UNi4B using the Heisenberg model. Considering the spin operators as classical vectors, we show that the classical ground state of this model is the vortexlike U spin arrangement in the basal plain. By means of the spin-wave method we calculate the temperature dependence of the specific heat at low temperatures, and estimate the coupling constants. From the obtained coupling constants we get the transition temperature TN=8.7 K.
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  • Spin Dynamics of the One-Dimensional J-J' Model and Spin-Peierls Transition in CuGeO3
    Hisatoshi Yokoyama, Yasuhiro Saiga
    Subject area: Magnetic properties and materials.
    1997 Volume 66 Issue 11 Pages 3617-3635
    Published: November 01, 1997
    Released on J-STAGE: October 01, 1999
    DOIhttps://doi.org/10.1143/jpsj.66.3617
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    Spin dynamics as well as static properties of the one-dimensionalJ-J' model (S=1/2, J>0 and 0≤ α=J'/J≤ 0.5) arestudied by the exact diagonalization and the recursion methodof finite systems up to 26 sites.Especially, the dynamical structure factor S(q, ω) isinvestigated carefully for various values of α.As α increases beyond the gapless-gapful critical valueαc=0.2411, there appear features definitely differentfrom the Heisenberg model but the same with the Majumdar-Ghosh model.Some of these features depend only on the value of α andnot on δ: a parameter introduced for the coupling alternation.By comparing these results with a recent inelastic neutron scatteringspectrum of an inorganic spin-Peierls compound CuGeO3[M. Arai et al.: Phys. Rev. Lett. 77 (1996) 3649], it is found thatthe frustration by J' in CuGeO3 is unexpectedly strong(α=0.4--0.45), and at least α must be larger thanαc to some extent.The value of J is evaluated at -- 180 K consistent with other estimations.The coupling alternation is extremely small.This large frustration is a primary origin of the various anomalousproperties CuGeO3 possesses.For comparison we refer also to α'-NaV2O5.
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  • Magnetization Process of the Mixed Compound with Exchange Frustrations Fe0.65Mn0.35TiO3 and Fe0.50Mn0.50TiO3 --Anomalous Dependence on the Sweep-Rate of Magnetic Fields
    Atsuko Ito, Chiyuki Oyama, Atsuko Fukaya, Hiroaki Kato, Shigeto Miura
    Subject area: Magnetic properties and materials.
    1997 Volume 66 Issue 11 Pages 3636-3647
    Published: November 01, 1997
    Released on J-STAGE: October 01, 1999
    DOIhttps://doi.org/10.1143/jpsj.66.3636
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    The magnetization processes of the spin-glass Fe0.50Mn0.50TiO3 and the reentrant spin-glass Fe0.65Mn0.35TiO3 have been measured in the magnetic field H swept with various sweep-rates between 0.050, T/s and 0.750, T/s at 4.2, K and -- 1.4, K. When H is swept up or down fast beyond a critical value of the sweep-rate, the anomalous jump-up and jump-down of the magnetization occurs towards the values of the field-cooled-magnetization. The jump-up or jump-down field of the magnetization changes depending on the sweep-rate and the temperature. It is demonstrated that the hysteresis related to the jump of the magnetization becomes small gradually with increasing the sweep-rate, which is opposite to the normal behavior that the response of spin systems is delayed for a fast sweep of H. We consider that these phenomena are closely related to the properties of the spin-glass state.
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  • Phase Transitions in Bilayer Heisenberg Model with General Couplings
    Yasuhiro Matsushita, Martin P. Gelf, Chikara Ishii
    Subject area: Magnetic properties and materials.
    1997 Volume 66 Issue 11 Pages 3648-3654
    Published: November 01, 1997
    Released on J-STAGE: October 01, 1999
    DOIhttps://doi.org/10.1143/jpsj.66.3648
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    The ground state properties and phase diagram of bilayer Heisenberg model on the square lattice are studied in a wide range of parameter space of intralayer exchange couplings, assuming an antiferromagnetic coupling between constituent layers. In the classical limit, the model exhibits three phases: two of these are ordered phases specified by the ordering wave vectors (π, π;π) and (0, 0;π), where the third component of each indecates the antiferromagnetic orientation between layers, and another one is “canted” phase, stabilized by competing interactions. The effects of quantum fluctuations in the model with S=1/2 have been explored in terms of dimer mean-field theory, exact diagonalization of 2√2×2√2×2 clusters, and higher-order perturbation expansions about the interlayer dimer limit.
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  • Nuclear Relaxation of Hydrogen-Doped Antiferromagnetic YBa2Cu3O6+{x}Hy
    Haruo Niki, Katsuji Tamaki, Kikuhiro Kano, Takeshi Shinohara, Shoichi ...
    Subject area: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
    1997 Volume 66 Issue 11 Pages 3655-3659
    Published: November 01, 1997
    Released on J-STAGE: October 01, 1999
    DOIhttps://doi.org/10.1143/jpsj.66.3655
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    Cu(1) NQR, Cu(2) zero field NMR, and proton NMR have been measured in the antiferromagnetic (AF) phase of a powdered sample of hydrogen-doped YBa2Cu3O6.1H0.14 from 4.2 to 300, K. The line width of 1H NMR increases abruptly below 20, K. The enhancements of T2-1 and T1-1 of 63Cu(1) NQR occur around 20 and 40, K, respectively. The relaxation mechanism of T1 of NQR changes at Trm=80, K and the time dependence of its nuclear magnetization recovery shows a nonexponential type for Trm and an exponential one for T>Trm. The predominant source for T1 below Trm is found to be the fluctuating magnetic fields due to the staggered Cu2+ moments induced by the hole doping effect. Above Trm, T1-1 of NQR increases gradually with temperature but it is almost temperature independent above 150, K, what can not be explained by the effect of the ordered AF Cu2+ moments in the Cu(2)O2 plane and also by the Raman process of the lattice vibrations.
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  • ESR Studies on CaV4O9 and CaV3O7
    Satoshi Taniguchi, Yoshiaki Kobayashi, Mayumi Kasai, Katsuaki Kodama, ...
    Subject area: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
    1997 Volume 66 Issue 11 Pages 3660-3664
    Published: November 01, 1997
    Released on J-STAGE: October 01, 1999
    DOIhttps://doi.org/10.1143/jpsj.66.3660
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    ESR measurements have been performed on single crystals of two-dimensional S=1/2 systems of CaV4O9 and CaV3O7.The linewidths of their ESR spectra can be described by the form of ( A cos 2 θ + B ), where θ is the angle between the directions of the c-axis and the external magnetic field and A and B are material dependent positive constants.The results seem to be understood by introducing the broadening due to the Dzyaloshinsky-Moriya interaction with exchange narrowing.The resonance field has been found to depend not only on θ but also on the angle between the directions of the c-axis and the microwave field.This behavior seems to be explained by considering the effect of the non-diagonal dynamical susceptibility expected for systems with low symmetry.
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  • Dielectric Spectrometry of Amorphous Thermoplastic/Glass Bead Composites
    Mourad Arous, Ali Kallel, Zouheir Fakhfakh, Gérard Perrier
    Subject area: Dielectric properties and materials.
    1997 Volume 66 Issue 11 Pages 3665-3667
    Published: November 01, 1997
    Released on J-STAGE: October 01, 1999
    DOIhttps://doi.org/10.1143/jpsj.66.3665
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    A series of polystyrene/glass bead and poly (styrene-co-methacrylic acid)/glass bead composites with volumic fractions in the order of 21\studied by means of dielectric spectrometry. Experimental isochronal data on the pure matrixes show the α relaxation, associated to the glass transition. In the case of the composites, a more intense relaxation appears at a higher temperature compared with that of the α relaxation. This relaxation is attributed to the Maxwell-Wagner-Sillars (MWS) effect. Experimental results are in agreement with the van Beek theory in the case of untreated spherical inclusions. This agreement is more remarkable in the case of coupling agent-treated glass beads.
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  • High Harmonics in Prototype Undulation. Related U-Ferroelectricity and U-Ferroelasticity
    Kêiichiro Aizu
    Subject area: Dielectric properties and materials.
    1997 Volume 66 Issue 11 Pages 3668-3672
    Published: November 01, 1997
    Released on J-STAGE: October 01, 1999
    DOIhttps://doi.org/10.1143/jpsj.66.3668
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    This paper performs the first investigation of high harmonics in prototype undulation. It also deals with U-ferroelectricity and U-ferroelasticity. [U- (or H-) ferroelectricity is ferroelectricity that should (or should not) vanish if the prototypic phase is brought from undulated to homogeneous.] For simplicity, only the second harmonic is taken into account, and no higher ones. Two cases are studied. They are the same in that the point group of the prototypic phase when homogeneous is mmm, the number of declension parameters is one and the expression of undulation of this parameter is δ =U1 cos (ĥx +\hat{θ}1)+U2 cos (2ĥx+\hat{θ}2). The two cases are different with regard to order-parameter symmetry. It is found that, if and only if U1≠ 0, U2≠ 0 and sin (\hat{θ}2-2\hat{θ}1)≠ 0, U-ferroelasticity occurs in one of the two cases, and U-ferroelectricity occurs (and is fast coupled with H-ferroelasticity) in the other case.
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  • Radiative Decay of Sm 4d-Hole States in Mixed-Valence SmB6
    Takashi Umehara, Kouichi Ichikawa, Osamu Aita, Kenjiro Tsutsumi
    Subject area: Optical properties and condensedmatter spectroscopy and other interactions of matter with particles and radiation.
    1997 Volume 66 Issue 11 Pages 3673-3677
    Published: November 01, 1997
    Released on J-STAGE: October 01, 1999
    DOIhttps://doi.org/10.1143/jpsj.66.3673
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    The Sm N4, 5 soft X-ray emission spectrum of mixed-valence SmB6 was measured to investigate the radiative decay of Sm 4d-hole states. For comparison, Sm N4, 5 absorption spectrum of SmB6 and Sm N4, 5 emission spectrum of Sm metal were measured. It is found that the emission spectrum of SmB6 is mainly composed of two types of 4f → 4d emission processes derived from Sm3+, 4d94f5 → 4d104f4+hν and 4d94f6 → 4d104f5+hν '. The detailed comparisons between these spectra and existent resonant photoemission spectra reveal the indications of radiative decay derived from Sm2+. In the N4, 5 region, no appreciable difference was found between probabilities of radiative decay of Sm3+ and Sm2+.
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  • Optical Spectra in the Ferromagnetic States near the Charge Ordering
    Sumio Ishihara, Naoto Nagaosa
    Subject area: Optical properties and condensedmatter spectroscopy and other interactions of matter with particles and radiation.
    1997 Volume 66 Issue 11 Pages 3678-3682
    Published: November 01, 1997
    Released on J-STAGE: October 01, 1999
    DOIhttps://doi.org/10.1143/jpsj.66.3678
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    The optical conductivity is studied numerically for the ferromagnetic metallic state close to the charge ordering observed in perovskite manganites. We focus on roles of the charge fluctuation on the incoherent component in the optical spectra, and consider the Coulomb interaction in the one- and two-dimensional spinless fermion models. The numerical results show that the incoherent part is not noticeable, and near the quarter-filling, most of the spectral weights are transferred to the Drude component. The discrepancy between our calculations and the experiments suggests that the orbital degrees of freedom play important roles.
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  • One-Dimensional Fukui-Ishibashi Traffic Flow Model
    Bing–Hong Wang, Lei Wang, P. M. Hui
    Subject area: Statistical physics and thermodynamics.
    1997 Volume 66 Issue 11 Pages 3683-3684
    Published: November 01, 1997
    Released on J-STAGE: October 01, 1999
    DOIhttps://doi.org/10.1143/jpsj.66.3683
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  • Giant Magnetoresistance of Eu/Se Superlattice
    Takafumi Ono, Naoki Sato, Tomohiko Ishii, Sei–ichi Tanuma, Ikush ...
    Subject area: Electronic structure and electrical properties of surfaces, interfaces and thin films.
    1997 Volume 66 Issue 11 Pages 3685-3686
    Published: November 01, 1997
    Released on J-STAGE: October 01, 1999
    DOIhttps://doi.org/10.1143/jpsj.66.3685
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  • A Theoretical Study of Magnons for Heisenberg Model in Triangulated Kagomé Lattice -Characteristic Dispersionless Modes-
    Ryo Natori, Yuichi Watabe, Yuhei Natsume
    Subject area: Magnetic properties and materials.
    1997 Volume 66 Issue 11 Pages 3687-3688
    Published: November 01, 1997
    Released on J-STAGE: October 01, 1999
    DOIhttps://doi.org/10.1143/jpsj.66.3687
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  • Magnetic Susceptibility of[Cu2(C2O4)(C10H8N2)2](NO4)2 --- a Candidate for a Spin Ladder Compound
    Zentaro Honda, Yoshihiko Nonomura, Koichi Katsumata
    Subject area: Magnetic properties and materials.
    1997 Volume 66 Issue 11 Pages 3689-3690
    Published: November 01, 1997
    Released on J-STAGE: October 01, 1999
    DOIhttps://doi.org/10.1143/jpsj.66.3689
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