574 research outputs found

    Magnetic Excitations in the Quasi-1D Ising-like Antiferromagnet TlCoCl3_3

    Full text link
    Neutron inelastic scattering measurements have been performed in order to investigate the magnetic excitations in the quasi-1D Ising-like antiferromagnet TlCoCl3_3. We observed the magnetic excitation, which corresponds to the spin-wave excitation continuum corresponding to the domain-wall pair excitation in the 1D Ising-like antiferromagnet. According to the Ishimura-Shiba theory, we analyzed the observed spin-wave excitation, and the exchange constant 2J2J and the anistropy ϵ\epsilon were estimated as 14.7 meV and 0.14 in TlCoCl3_3, respectively.Comment: 2 pages, 3 figures, jpsj2.cls, to be published in J. Phys. Soc. Jpn. Vol.75 (2006) No.

    Spin dynamics of a one-dimensional spin-1/2 fully anisotropic Ising-like antiferromagnet in a transverse magnetic field

    Full text link
    We consider the one-dimensional Ising-like fully anisotropic S=1/2 Heisenberg antiferromagnetic Hamiltonian and study the dynamics of domain wall excitations in the presence of transverse magnetic field hxh_x. We obtain dynamical spin correlation functions along the magnetic field Sxx(q,ω)S^{xx}(q,\omega) and perpendicular to it Syy(q,ω)S^{yy}(q,\omega). It is shown that the line shapes of Sxx(q,ω)S^{xx}(q,\omega) and Syy(q,ω)S^{yy}(q,\omega) are purely symmetric at the zone-boundary. It is observed in Syy(q,ω)S^{yy}(q,\omega) for π/2<q<π\pi/2<q<\pi that the spectral weight moves toward low energy side with the increase of hxh_x. This model is applicable to study the spin dynamics of CsCoCl3_3 in the presence of weak interchain interactions.Comment: 19 pages, LaTeX, 12 eps figure

    Polarized Neutron Inelastic Scattering Study of the Anisotropic Magnetic Fluctuations in the Quasi-1D Ising-like Antiferromagnet TlCoCl3_3

    Full text link
    Polarized neutron inelastic scattering experiments have been carried out in the quasi-1D Ising-like antiferromagnet TlCoCl3_3. We observed the longitudinal magnetic fluctuation Szz(Q,ω)S_{zz} (Q, \omega) for the spin-wave excitation continuum, which has not been observed in the unpolarized neutron inelastic scattering experiments of the quasi-1D Ising-like antiferromagnets CsCoCl3_3 and TlCoCl3_3 so far, together with the transverse magnetic fluctuation Sxx(Q,ω)S_{xx} (Q, \omega). We compared both obtained intensities of Sxx(Q,ω)S_{xx} (Q, \omega) and Szz(Q,ω)S_{zz} (Q, \omega) with the perturbation theory from the pure Ising limit by Ishimura and Shiba, and a semi-quantitative agreement was found.Comment: 5 pages, 5 figures, jpsj2.cls, to be published in J. Phys. Soc. Jpn. Vol. 75 (2006) No.

    The IntraCluster Medium: An Invariant Stellar IMF

    Get PDF
    Evidence supporting the hypothesis of an invariant stellar Initial Mass Function is strong and varied. The intra-cluster medium in rich clusters of galaxies is one of the few contrary locations where recent interpretations of the chemical abundances have favoured an IMF that is biased towards massive stars, compared to the `normal' IMF. This interpretation hinges upon the neglect of Type Ia supernovae to the ICM enrichment, and a particular choice of the nucleosynthesis yields of Type II supernovae. We demonstrate here that when one adopts yields determined empirically from observations of Galactic stars, rather than the uncertain model yields, a self-consistent picture may be obtained with an invariant stellar IMF, and about half of the iron in the ICM being produced by Type Ia supernovae.Comment: 9 pages, LateX (aaspp4 macro), including one postscript figure. Accepted, ApJ Letter

    Dynamical Structure Factors of the S=1/2 Bond-Alternating Spin Chain with a Next-Nearest-Neighbor Interaction in Magnetic Fields

    Full text link
    The dynamical structure factor of the S=1/2 bond-alternating spin chain with a next-nearest-neighbor interaction in magnetic field is investigated using the continued fraction method based on the Lanczos algorithm. When the plateau exists on the magnetization curve, the longitudinal dynamical structure factor shows a large intensity with a periodic dispersion relation, while the transverse one shows a large intensity with an almost dispersionless mode. The periodicity and the amplitude of the dispersion relation in the longitudinal dynamical structure factor are sensitive to the coupling constants. The dynamical structure factor of the S=1/2 two-leg ladder in magnetic field is also calculated in the strong interchain-coupling regime. The dynamical structure factor shows gapless or gapful behavior depending on the wave vector along the rung.Comment: 8 pages, 4 figures, to appear in Journal of the Physical Society of Japan, vol. 69, no. 10, (2000

    Thermodynamic Properties and Elementary Excitations in Quantum Sine-Gordon Spin System KCuGaF6

    Full text link
    Thermodynamic properties and elementary excitations in S=1/2S=1/2 one-dimensional Heisenberg antiferromagnet KCuGaF6_6 were investigated by magnetic susceptibility, specific heat and ESR measurements. Due to the Dzyaloshinsky-Moriya interaction with alternating DD-vectors and/or the staggered gg-tensor, the staggered magnetic field is induced when subjected to external magnetic field. Specific heat in magnetic field clearly shows the formation of excitation gap, which is attributed to the staggered magnetic field. The specific heat data was analyzed on the basis of the quantum sine-Gordon (SG) model. We observed many ESR modes including one soliton and three breather excitations characteristic of the quantum SG model.Comment: 4 pages, 5 figures, to appear in J. Phys. Soc. Jpn., vol. 76, no.

    Slip-partitioned surface ruptures for the Mw 7.0 16 April 2016 Kumamoto, Japan, earthquake

    Get PDF
    An ENE-trending ~30-km-long surface rupture emerged during the Mw = 7.0 16 April 2016 Kumamoto earthquake along the previously mapped Futagawa and northern Hinagu faults. This included a previously unknown 5-km-long fault within the Aso Caldera, central Kyushu. The rupture zone is mostly composed of right-lateral slip sections, with a maximum of 2-m coseismic slip. One of the noteworthy features we observed in the field are ~10-km-long segmented normal fault scarps, dipping to the northwest, along the previously mapped Idenokuchi fault, 1.2–2.0 km south of and subparallel to the Futagawa fault. The maximum amount of coseismic throw on the Idenokuchi fault is ~2 m, which is nearly equivalent to the maximum slip on the strike-slip rupture. The locations and slip motions of the 2016 rupture are also manifested as interferogram fringe offsets in InSAR images. Together with geodetic and seismic inversions of subsurface fault slip, we present a schematic structural model where oblique motion occurred on a northwest-dipping subsurface fault and the slip is partitioned at the surface into strike-slip and normal fault scarps. Our simple dislocation model demonstrates that this bifurcation into pure strike-slip and normal faults likely occurs for optimally oriented failure near the surface. The Kumamoto case, with detailed geological observations and geophysical models, would be the second significant slip-partitioned earthquake around the globe. It provides an important insight into scale- and depth-dependent stress heterogeneity and an implication to a proper estimate of seismic hazard in complex and broad multiple fault strands

    Dynamical Structure Factors of the Spin-1/2 XXZ Chain with Inverse-Square Exchange and Ising Anisotropy

    Full text link
    The dynamical properties of the S=1/2 antiferromagnetic XXZ chain are studied by the exact diagonalization and the recursion method of finite systems up to 24 sites. Two types of the exchange interaction are considered: one is the nearest-neighbor type, and the other is the inverse-square one. As the Ising anisotropy becomes larger, there appears a noticeable difference in the transverse component S^{xx}(q,\omega) between the two types of the exchange. For the nearest-neighbor type, the peak frequency of S^{xx}(q,\omega) for each q approaches the center of the continuum spectrum. On the contrary, the peak frequency for the inverse-square type moves to the upper edge of the continuum, and separates from the continuum for the anisotropy larger than the threshold value. Whether the interaction between domain walls (solitons) is absent or repulsive in the Ising limit leads to this difference in the behavior of S^{xx}(q,\omega). In the longitudinal component S^{zz}(q,\omega), on the other hand, the feature of the dynamics is scarcely different between the two types. The energy gap and the static properties are also discussed.Comment: 10 pages. A hard copy of 16 figures is available on request. Submitted to J. Phys. Soc. Jp

    Direct Observation of Field-Induced Incommensurate Fluctuations in a One-Dimensional S=1/2 Antiferromagnet

    Full text link
    Neutron scattering from copper benzoate, Cu(C6D5COO)2 3D2O, provides the first direct experimental evidence for field-dependent incommensurate low energy modes in a one-dimensional spin S = 1/2 antiferromagnet. Soft modes occur for wavevectors q=\pi +- dq(H) where dq(H) ~ 2 \pi M(H)/g\mu_B as predicted by Bethe ansatz and spinon descriptions of the S = 1/2 chain. Unexpected was a field-induced energy gap Δ(H)Hα\Delta(H) \propto H^\alpha, where α=0.65(3)\alpha = 0.65(3) as determined from specific heat measurements. At H = 7 T (g\mu_B H/J = 0.52), the magnitude of the gap varies from 0.06 - 0.3 J depending on the orientation of the applied field.Comment: 11 pages, 5 postscript figures, LaTeX, Submitted to PRL 3/31/97, e-mail comments to [email protected]
    corecore