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

Neutron inelastic scattering measurements have been performed in order to investigate the magnetic excitations in the quasi-1D Ising-like antiferromagnet TlCoCl$_3$. 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 $2J$ and the anistropy $\epsilon$ were estimated as 14.7 meV and 0.14 in TlCoCl$_3$, respectively.Comment: 2 pages, 3 figures, jpsj2.cls, to be published in J. Phys. Soc. Jpn. Vol.75 (2006) No.

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

Polarized neutron inelastic scattering experiments have been carried out in the quasi-1D Ising-like antiferromagnet TlCoCl$_3$. We observed the longitudinal magnetic fluctuation $S_{zz} (Q, \omega)$ 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 CsCoCl$_3$ and TlCoCl$_3$ so far, together with the transverse magnetic fluctuation $S_{xx} (Q, \omega)$. We compared both obtained intensities of $S_{xx} (Q, \omega)$ and $S_{zz} (Q, \omega)$ 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.

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

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

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

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 $h_x$. We obtain dynamical spin correlation functions along the magnetic field $S^{xx}(q,\omega)$ and perpendicular to it $S^{yy}(q,\omega)$. It is shown that the line shapes of $S^{xx}(q,\omega)$ and $S^{yy}(q,\omega)$ are purely symmetric at the zone-boundary. It is observed in $S^{yy}(q,\omega)$ for $\pi/2<q<\pi$ that the spectral weight moves toward low energy side with the increase of $h_x$. This model is applicable to study the spin dynamics of CsCoCl$_3$ in the presence of weak interchain interactions.Comment: 19 pages, LaTeX, 12 eps figure

The IntraCluster Medium: An Invariant Stellar IMF

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

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

Thermodynamic properties and elementary excitations in $S=1/2$ one-dimensional Heisenberg antiferromagnet KCuGaF$_6$ were investigated by magnetic susceptibility, specific heat and ESR measurements. Due to the Dzyaloshinsky-Moriya interaction with alternating $D$-vectors and/or the staggered $g$-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.

Ground states of a one-dimensional lattice-gas model with an infinite range nonconvex interaction. A numerical study

We consider a lattice-gas model with an infinite range pairwise noncovex interaction. It might be relevant, for example, for adsorption of alkaline elements on W(112) and Mo(112). We study a competition between the effective dipole-dipole and indirect interactions. The resulting ground state phase diagrams are analysed (numerically) in detail. We have found that for some model parameters the phase diagrams contain a region dominated by several phases only with periods up to nine lattice constants. The remaining phase diagrams reveal a complex structure of usually long periodic phases. We also discuss a possible role of surace states in phase transitions.Comment: 16 pages, 5 Postscript figures; Physical Review B15 (15 August 1996), in pres

Fractional S^z excitation and its bound state around the 1/3 plateau of the S=1/2 Ising-like zigzag XXZ chain

We present the microscopic view for the excitations around the 1/3 plateau state of the Ising-like zigzag XXZ chain. We analyze the low-energy excitations around the plateau with the degenerating perturbation theory from the Ising limit, combined with the Bethe-form wave function. We then find that the domain-wall particles carrying $S^z=\pm 1/3$ and its bound state of $S^z=\pm 2/3$ describe well the low-energy excitations around the 1/3 plateau state. The formation of the bound state of the domain-walls clearly provides the microscopic mechanism of the cusp singularities and the even-odd behavior in the magnetization curve.Comment: 13 pages, 15 figure

The GRB 071112C: A Case Study of Different Mechanisms in X-ray and Optical Temporal Evolution

We present the study on GRB 071112C X-ray and optical light curves. In these two wavelength ranges, we have found different temporal properties. The R-band light curve showed an initial rise followed by a single power-law decay, while the X-ray light curve was described by a single power-law decay plus a flare-like feature. Our analysis shows that the observed temporal evolution cannot be described by the external shock model in which the X-ray and optical emission are produced by the same emission mechanism. No significant color changes in multi-band light curves and a reasonable value of the initial Lorentz factor ({\Gamma}0 = 275 \pm 20) in a uniform ISM support the afterglow onset scenario as the correct interpretation for the early R-band rise. The result suggests the optical flux is dominated by afterglow. Our further investigations show that the X-ray flux could be created by an additional feature related to energy injection and X-ray afterglow. Different theoretical interpretations indicate the additional feature in X-ray can be explained by either late internal dissipation or local inverse-Compton scattering in the external shock.Comment: 20 pages, 3 figures, accepted for publication in Ap