6,765 research outputs found
Comment on ``Spin-glass transition of the three-dimensional Heisenberg spin glass''
Campos et al. [Phys. Rev. Lett. 97 (2006) 217204] claim that in the 3d
Heisenberg Spin Glass, chiral and spin sector ordering temperatures are
identical. We point out that in their analysis of their numerical data key
assumptions are made which are unjustified.Comment: published versio
Amorphous Vortex Glass Phase in Strongly Disordered Superconductors
We introduce a model describing vortices in strongly disordered
three-dimensional superconductors. The model focuses on the topological
defects, i.e., dislocation lines, in an elastic description of the vortex
lattice. The model is studied using Monte Carlo simulations, revealing a glass
phase at low temperatures, separated by a continuous phase transition to the
high temperature resistive vortex liquid phase. The critical exponents nu ~ 1.3
and eta ~ -0.4 characterizing the transition are obtained from finite size
scaling.Comment: 4 pages, 4 figure
First-Order Transition to Incommensurate Phase with Broken Lattice Rotation Symmetry in Frustrated Heisenberg Model
We study a finite-temperature phase transition in the two-dimensional
classical Heisenberg model on a triangular lattice with a ferromagnetic
nearest-neighbor interaction and an antiferromagnetic
third-nearest-neighbor interaction using a Monte Carlo method. Apart from
a trivial degeneracy corresponding to O(3) spin rotations,the ground state for
has a threefold degeneracy corresponding to 120 degree lattice
rotations. We find that this model exhibits a first-order phase transition with
the breaking of the threefold symmetry when the interaction ratio is
.Comment: 4pages,5figure
Spin and chirality orderings of the one-dimensional Heisenberg spin glass with the long-range power-law interaction
The ordering of the one-dimensional Heisenberg spin glass interacting via the
long-range power-law interaction is studied by Monte Carlo simulations.
Particular attention is paid to the possible occurrence of the ``spin-chirality
decoupling'' for appropriate values of the power-law exponent \sigma. Our
result suggests that, for intermediate values of , the chiral-glass
order occurs at finite temperatures while the standard spin-glass order occurs
only at zero temperature.Comment: Proceedings of the Highly Frustrated Magnetism (HFM2006) conference.
To appear in a special issue of J. Phys. Condens. Matte
Chirality scenario of the spin-glass ordering
Detailed account is given of the chirality scenario of experimental
spin-glass transitions. In this scenario, the spin glass order of weakly
anisotropic Heisenberg-like spin-glass magnets including canonical spin glasses
are essentially chirality driven. Recent numerical and experimental results are
discussed in conjunction with this scenario.Comment: Submitted to J. Phys. Soc. Japan "Special Issue on Frustration
Monte Carlo studies of the ordering of the one-dimensional Heisenberg spin glass with long-range power-law interactions
The nature of the ordering of the one-dimensional Heisenberg spin-glass model
with a long-range power-law interaction is studied by extensive Monte Carlo
simulations, with particular attention to the issue of the spin-chirality
decoupling/coupling. Large system sizes up to are studied. With
varying the exponent describing the power-law interaction, we observe
three distinct types of ordering regimes. For smaller , the spin and
the chirality order at a common finite temperature with a common
correlation-length exponent, exhibiting the standard spin-chirality coupling
behavior. For intermediate , the chirality orders at a temperature
higher than the spin, exhibiting the spin-chirality decoupling behavior. For
larger , both the spin and the chirality order at zero temperature. We
construct a phase diagram in the versus the temperature plane, and
discuss implications of the results. Critical properties associated with both
the chiral-glass and the spin-glass transitions are also determined.Comment: 28 pages, 26 figures, to appear in J. Phys. Soc. Jp
Ordering in a spin glass under applied magnetic field
Torque, torque relaxation, and magnetization measurements on a AuFe spin
glass sample are reported. The experiments carried out up to 7 T show a
transverse irreversibility line in the (H,T) plane up to high applied fields,
and a distinct strong longitudinal irreversibility line at lower fields. The
data demonstrate for that this type of sample, a Heisenberg spin glass with
moderately strong anisotropy, the spin glass ordered state survives under high
applied fields in contrast to predictions of certain "droplet" type scaling
models. The overall phase diagram closely ressembles those of mean field or
chiral models, which both have replica symmetry breaking transitions.Comment: 4 pages, 3 figures, accepted for PR
High Field ESR and Magnetization of the Triangular Lattice Antiferromagnet NiGa2S4
We report the experimental and the analytical results of electron spin
resonance (ESR) and magnetization in high magnetic fields up to about 68 T of
the quasi two-dimensional triangular lattice antiferromagnet NiGaS.
From the temperature evolution of the ESR absorption linewidth, we find a
distinct disturbing of the development of the spin correlation by
-vortices between 23 K and 8.5 K. Below K, spin-wave
calculations based on a 57 spiral spin order well explains the
frequency dependence of the ESR resonance fields and high field magnetization
processes for and , although the magnetization
for at high fields is different from the calculated one.
Furthermore, we explain the field independent specific heat with
-dependence by the same spin-wave calculation, but the magnitude of the
specific heat is much less than the observed one. Accordingly, these results
suggest the occurrence of a vortex-induced topological transition at
and may indicate quantum effects beyond the descriptions based on
the above classical spin models
Analysis and Future Estimation of Medical Demands Using a Health Care Simulation Model: A Case Study of Japan
A method of building a universal health care model was proposed in RM-77-006 (Kaihara, et al., An Approach to Building a Universal Health Care Model). This method is based on the calculation of essential parameters of health care from ordinary statistics. The essential parameters proposed in the previous report were population structure, morbidity rate, recovery rate, death rate, patient registration rate and awareness rate.
The method was applied successfully to the analysis of medical demands at the national level of Japan. The results showed that in the past 15 years the awareness rate was the most important factor which contributed to the increase of the patients. But in the future, the model predicted that the change of population structure will be the main cause of the increase of the number of patients in Japan
Oceanographic Data in Lutzow-Holm Bay of the Antarctic Climate Research Program from January 1991 to February 1992 (JARE-32)
- …