T. Masuda

Two-stage spin-flop transitions in the S = 1/2 antiferromagnetic spin chain BaCu(2)Si(2)O(7).

Two-stage spin-flop transitions are observed in the quasi-one-dimensional antiferromagnet BaCu(2)Si(2)O(7). A magnetic field applied along the easy axis induces a spin-flop transition at 2.0 T followed by a second transition at 4.9 T. The magnetic susceptibility indicates the presence of Dzyaloshinskii-Moriya (DM) antisymmetric interactions between the intrachain neighboring spins. We discuss a possible mechanism whereby the geometrical competition between DM and interchain interactions, as discussed for the two-dimensional antiferromagnet La(2)CuO(4), causes the two-stage spin-flop transitions.

Magnetic anisotropy and low-energy spin waves in the Dzyaloshinskii-Moriya spiral magnet Ba{sub 2}CuGe{sub 2}O{sub 7}

Neutron-diffraction and inelastic-scattering experiments are used to investigate in detail the field dependence of the magnetic structure and low-energy spin-wave spectrum of the Dzyaloshinskii-Moriya helimagnet Ba{sub 2}CuGe{sub 2}O{sub 7}. The results suggest that the previously proposed model for the magnetism of this compound (an ideal sinusoidal spin spiral, stabilized by isotropic exchange and Dzyaloshinskii-Moriya interactions) needs to be refined. Both recent and previously published data can be quantitatively explained by taking into account the Kaplan-Shekhtman-Entin-Wohlman-Aharony term, a special magnetic anisotropy term that was predicted to always accompany Dzyaloshinskii-Moriya interactions in insulators. {copyright} {ital 1999} {ital The American Physical Society}

Critical bottleneck size for jamless particle flows in two dimensions.

We propose a simple microscopic model for arching phenomena at bottlenecks. The dynamics of particles in front of a bottleneck is described by a one-dimensional stochastic cellular automaton on a semicircular geometry. The model reproduces oscillation phenomena due to the formation and collapsing of arches. It predicts the existence of a critical bottleneck size for continuous particle flows. The dependence of the jamming probability on the system size is approximated by the Gompertz function. The analytical results are in good agreement with simulations.

Weak ferromagnetism of quasi-one-dimensional S = 1 2 antiferromagnet BaCu 2 Ge 2 O 7

Weak ferromagnetism of quasi-one-dimensional

First-order phase transition between dimerized-antiferromagnetic and uniform-antiferromagnetic phases inCu1−xMxGeO3

S=\frac{1}{2}

STRUCTURAL CRITICAL SCATTERING STUDY OF MG-DOPED CUGEO3

antiferromagnet

Magnetic property of Ba2CoGe2O7

{\mathrm{BaCu}}_{2}{\mathrm{Ge}}_{2}{\mathrm{O}}_{7}

Thermal conductivity of Mg-doped CuGeO 3

is studied by the magnetization measurement. The spontaneous magnetization appears along the b axis below 8.8 K. The local symmetry between the intrachain nearest-neighbor spins allows the presence of the Dzyaloshinskii-Moriya interaction, and the only possible spatial configuration of the weak ferromagnetic moment per spin definitely determines the sign of the interchain interaction. A weak a-axis magnetic field can change the direction of the magnetization to the a-axis direction, which shows that the spin chain forms a weakly coupled weak-ferromagnetic chain system.

Experimental evidence for kaplan-shekhtman-entin-wohlman-aharony interactions in Ba2CuGe2O7

We have performed detailed magnetic susceptibility measurements as well as synchrotron x-ray diffraction studies to determine the temperature vs concentration (

Thermal conductivity of Mg-doped CuGeO 3 at very low temperatures: Heat conduction by antiferromagnetic magnons

T