6,739 research outputs found
Magnetic Susceptibility for
We examine experimental magnetic susceptibility for
CaVO by fitting with fitting function .
The function is a power series of 1/T and the lowest order
term is fixed as , where is the Curie constant as determined by the
experimental -value (g=1.96). Fitting parameters are , and
expansion coefficients except for the first one in .
We determine and as 0.73 and 0 for an
experimental sample. We interpret as the volume fraction of
CaVO in the sample and as the susceptibility for the
pure CaVO. The result of means that the sample includes
nonmagnetic components. This interpretation consists with the result of a
perturbation theory and a neutron scattering experiment.Comment: 4pages, 4figure
Viscoelastic response of contractile filament bundles
The actin cytoskeleton of adherent tissue cells often condenses into filament
bundles contracted by myosin motors, so-called stress fibers, which play a
crucial role in the mechanical interaction of cells with their environment.
Stress fibers are usually attached to their environment at the endpoints, but
possibly also along their whole length. We introduce a theoretical model for
such contractile filament bundles which combines passive viscoelasticity with
active contractility. The model equations are solved analytically for two
different types of boundary conditions. A free boundary corresponds to stress
fiber contraction dynamics after laser surgery and results in good agreement
with experimental data. Imposing cyclic varying boundary forces allows us to
calculate the complex modulus of a single stress fiber.Comment: Revtex with 24 pages, 7 Postscript figures included, accepted for
publication in Phys. Rev.
The Heisenberg model on the 1/5-depleted square lattice and the CaV4O9 compound
We investigate the ground state structure of the Heisenberg model on the
1/5-depleted square lattice for arbitrary values of the first- and
second-neighbor exchange couplings. By using a mean-field Schwinger-boson
approach we present a unified description of the rich ground-state diagram,
which include the plaquette and dimer resonant-valence-bond phases, an
incommensurate phase and other magnetic orders with complex magnetic unit
cells. We also discuss some implications of ours results for the experimental
realization of this model in the CaV4O9 compound.Comment: 4 pages, Latex, 7 figures included as eps file
Magnetic Phases of Frustrated Ferromagnetic Spin-Trimer System Gd_3_Ru_4_Al_12_ With a Distorted Kagome Lattice Structure
The magnetization and specific heat measurements have been performed on
single-crystalline Gd_3_Ru_4_Al_12_ with a distorted Kagome lattice structure.
This spin system is regarded as an antiferromagnetic triangular lattice of XY
like Heisenberg model at low temperatures. The magnetic phase diagrams indicate
the existence of frustration and Z_2_ degeneracy. The magnetization and
specific heat imply the successive phase transitions with partial disorder and
a T-shaped spin structure in the ground state.Comment: 14 pages, 19 figure
Orbital Order Effect of Two-Dimensional Spin Gap System for CaV4O9
Effects of possible orbital order in magnetic properties of two-dimensional
spin gap system for CaVO are investigated theoretically. After
analyzing experimental data, we show that single orbital models assumed in the
literature are insufficient to reproduce the data. To understand the origin of
the discrepancy, we assume that in state of V, and
orbitals have substantial contributions in the lowest-energy atomic level which
leads to a double-degeneracy. We study possible configurations of the orbital
order. By exact diagonalization and perturbation expansion, we calculate the
susceptibility, wavenumber dependence of low-lying excitations and equal-time
spin-spin correlations which is related to integrated intensity of the neutron
inelastic scattering. These quantities sensitively depend on the configuration
of the orbital order. The calculated results for some configurations of the
orbital order reproduce many experimental results much better than the previous
single-orbital models. However some discrepancy still remains to completely
reproduce all of the reported experimental results. To understand the origin of
these discrepancies, we point out the possible importance of the partially
occupied orbital in addition to orbital order of partially filled
and orbitals.Comment: 19 pages LATEX, 15 postscript figures, using jpsj.sty,to be published
in J.Phys.Soc.Jpn. Vol.67 No.2 (1998
Mechanisms for Non-Trivial Magnetization Plateaux of an S=1 Frustrated Spin Ladder
We investigate the non-trivial magnetization plateau at 1/4 of the saturation
magnetization of S=1 spin ladder, especially with reference to recent
experimental results on a new organic tetraradical
3,3',5,5'-tetrakis(N-tert-butylaminoxyl)biphenyl, abbreviated as BIP-TENO. We
propose three mechanisms for the formation of the plateau; the Neel mechanism,
the dimer mechanism and the spin-Peierls mechanism. We also discuss the effect
of four-spin exchange interactions.Comment: 3 pages, 5 figures, Orbital2001 (International Conference on Strongly
Correlated Electrons with Orbital Degrees of Freedom) (September 11-14, 2001.
Sendai
cemA homologue essential to CO2 transport in the cyanobacterium Synechocystis PCC6803.
Meta-Plaquette Expansion for the Triplet Excitation Spectrum in CaVO
We study antiferromagnetic, Heisenberg models with nearest and second
neighbor interactions on the one-fifth depleted square lattice which describes
the spin degrees of freedom in the spin-gap system CaVO. The
meta-plaquette expansion for the triplet excitation spectrum is extended to
fifth order, and the results are compared with experimental data on
CaVO. We attempt to locate the phase boundary between magnetically
ordered and gapped phases.Comment: 4 figure
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