1,751 research outputs found
Uniaxial pressure dependencies of the phase boundary of TlCuCl_3
We present a thermal expansion and magnetostriction study of TlCuCl_3, which
shows a magnetic-field induced transition from a spin gap phase to a Neel
ordered phase. Using Ehrenfest relations we derive huge and strongly
anisotropic uniaxial pressure dependencies of the respective phase boundary,
e.g. the transition field changes by about GPa depending on the
direction of uniaxial pressure.Comment: 2 pages, e figures; presented at SCES200
Pressure-Induced Magnetic Quantum Phase Transitions from Gapped Ground State in TlCuCl3
Magnetization maesurements under hydrostatic pressure were performed on an
S=1/2 coupled spin system TlCuCl3 with a gapped ground state under magnetic
field H parallel to the [2,0,1] direction. With increasing applied pressure P,
the gap decreases and closes completely at Pc=0.42 kbar. For P>Pc, TlCuCl3
undergoes antiferromagnetic ordering. A spin-flop transition was observed at
Hsf=0.7T. The spin-flop field is approximately independent of pressure,
although the sublattice magnetization increases with pressure. The gap and Neel
temperature are presented as function is attributed to to the relative
enhancement of the interdimer exchange interactions compared with the
intradimer exchange interaction.Comment: 4pages,3figures To be published in J. Phys. Soc. Jpn. Vol.73 No.1
Drastic Change of Magnetic Phase Diagram in Doped Quantum Antiferromagnet TlCuMgCl
TlCuCl is a coupled spin dimer system, which has a singlet ground state
with an excitation gap of = 5.5 T.
TlCuMgCl doped with nonmagnetic Mg ions undergoes
impurity-induced magnetic ordering. Because triplet excitation with a finite
gap still remains, this doped system can also undergo magnetic-field-induced
magnetic ordering. By specific heat measurements and neutron scattering
experiments under a magnetic field, we investigated the phase diagram in
TlCuMgCl with , and found that impurity- and
field-induced ordered phases are the same. The gapped spin liquid state
observed in pure TlCuCl is completely wiped out by the small amount of
doping.Comment: 9 pages, 5 figures, jpsj2 class file, to be published in J. Phy. Soc.
Jpn. Vol.75 No.3 (2006); layout changed, unrelated figure remove
Renormalized charge in a two-dimensional model of colloidal suspension from hypernetted chain approach
The renormalized charge of a simple two-dimensional model of colloidal
suspension was determined by solving the hypernetted chain approximation and
Ornstein-Zernike equations. At the infinite dilution limit, the asymptotic
behavior of the correlations functions is used to define the effective
interactions between the components of the system and these effective
interactions were compared to those derived from the Poisson-Boltzmann theory.
The results we obtained show that, in contrast to the mean-field theory, the
renormalized charge does not saturate, but exhibits a maximum value and then
decays monotonically as the bare charge increases. The results also suggest
that beyond the counterion layer near to the macroion surface, the ionic cloud
is not a diffuse layer which can be handled by means of the linearized theory,
as the two-state model claims, but a more complex structure is settled by the
correlations between microions
Finite-Width Bundle is Most Stable in a Solution with Salt
We applied the mean-field approach to a columnar bundle assembled by the
parallel arrangement of stiff polyelectrolyte rods in a salt bath. The
electrostatic potential can be divided into two regions: inside the bundle for
condensed counter-ions, and outside the bundle for free small ions. To
determine the distribution of condensed counter-ions inside the bundle, we use
a local self-consistent condition that depends on the charge density, the
electrostatic potential, and the net polarization. The results showed that,
upon bundle formation, the electric charge of polyelectrolytes, even those
inside the bundle, tend to survive in an inhomogeneous manner, and thus their
width remains finite under thermal equilibrium because of the long-range effect
of charge instability.Comment: 7 pages, 4 figure
Magentic-Field Induced Quantum Phase Transition and Critical Behavior in a Gapped Spin System TlCuCl
Magnetization measurements were performed on TlCuCl with gapped ground
state. The critical density and the magnetic phase diagram were obtained. The
interacting constant was obtained as K. The experimental
phase boundary for K agrees perfectly with the magnon BEC theory based
on the Hartree-Fock approximation with realistic dispersion relations and
K. The exponent obtained with all the data points
for K is , which is somewhat larger than theoretical
exponent . However, it was found that the exponent
converges at with decreasing fitting window.Comment: 2 pages, 2 figures, Submitted to Proceedings of International
Conference on Magnetism (ICM2006
Cloning of the C-terminal cytoplasmic fragment of the tar protein and effects of the fragment on chemotaxis of Escherichia coli
A gene encoding only the C-terminal portion of the receptor-transducer protein Tar of Escherichia coli was constructed. The gene product was detected and localized in the cytoplasmic fraction of the cell by immunoblotting with anti-Tar antibodies. The C-terminal fragments from wild-type and mutant tar genes were characterized in vivo. The C-terminal fragment generated from tar-526, a mutation that results in a dominant "tumble" phenotype, was found to be deamidated and methylated by the CheB and CheR proteins, respectively. The C-terminal fragment derived from a wild-type gene was poorly deamidated, and the C-terminal fragment derived from tar-529, a dominant mutant with a "smooth swimming" phenotype, was not apparently modified. Cells carrying the C-terminal fragment with the tar-526 mutation as the sole receptor-transducer protein showed a high frequency of tumbling and chemotaxis responses to changes in intracellular pH. These results suggest that the cytoplasmic C-terminal fragment of Tar retains some of the functions of the whole protein in vivo
Thermodynamics of the coupled spin-dimer system TlCuCl3 close to a quantum phase transition
We present thermal expansion alpha, magnetostriction and specific heat C
measurements of \tal, which shows a quantum phase transition from a spin-gap
phase to a Neel-ordered ground state as a function of magnetic field around
H_{C0}->4.8T. Using Ehrenfest's relation, we find huge pressure dependencies of
the spin gap for uniaxial as well as for hydrostatic pressure. For T->0 and
H->H_{C0} we observe a diverging Grueneisen parameter Gamma(T)=alpha/C, in
qualitative agreement with theoretical predictions. However, the predicted
individual temperature dependencies alpha(T) and C(T) are not reproduced by our
experimental data.Comment: 6 pages including 7 figures, contribution to the III Joint European
Magnetic Symposia 2006, San Sebastia
- …