111,070 research outputs found
Corrections to scaling in the dynamic approach to the phase transition with quenched disorder
With dynamic Monte Carlo simulations, we investigate the continuous phase
transition in the three-dimensional three-state random-bond Potts model. We
propose a useful technique to deal with the strong corrections to the dynamic
scaling form. The critical point, static exponents and , and
dynamic exponent are accurately determined. Particularly, the results
support that the exponent satisfies the lower bound .Comment: 10 pages, 6 figures, 2 table
Dynamic effect of overhangs and islands at the depinning transition in two-dimensional magnets
With the Monte Carlo methods, we systematically investigate the short-time
dynamics of domain-wall motion in the two-dimensional random-field Ising model
with a driving field ?DRFIM?. We accurately determine the depinning transition
field and critical exponents. Through two different definitions of the domain
interface, we examine the dynamics of overhangs and islands. At the depinning
transition, the dynamic effect of overhangs and islands reaches maximum. We
argue that this should be an important mechanism leading the DRFIM model to a
different universality class from the Edwards-Wilkinson equation with quenched
disorderComment: 9 pages, 6 figure
Understanding and Improving the Wang-Landau Algorithm
We present a mathematical analysis of the Wang-Landau algorithm, prove its
convergence, identify sources of errors and strategies for optimization. In
particular, we found the histogram increases uniformly with small fluctuation
after a stage of initial accumulation, and the statistical error is found to
scale as with the modification factor . This has implications
for strategies for obtaining fast convergence.Comment: 4 pages, 2 figures, to appear in Phys. Rev.
Critical domain-wall dynamics of model B
With Monte Carlo methods, we simulate the critical domain-wall dynamics of
model B, taking the two-dimensional Ising model as an example. In the
macroscopic short-time regime, a dynamic scaling form is revealed. Due to the
existence of the quasi-random walkers, the magnetization shows intrinsic
dependence on the lattice size . A new exponent which governs the
-dependence of the magnetization is measured to be .Comment: 10pages, 4 figure
Significance of interface anisotropy in laser induced magnetization precession in ferromagnetic metal films
Laser induced ultrafast demagnetization in ferromagnetic metals was
discovered almost 20 years ago, but currently there is still lack of consensus
on the microscopic mechanism responsible for the corresponding transfer of
angular momentum and energy between electron, lattice and spin subsystems. A
distinct, but intrinsically correlated phenomenon occurring on a longer
timescale is the magnetization precession after the ultrafast demagnetization
process, if a magnetic field is applied to tilt the magnetization vector away
from its easy direction, which can be attributed to the change of anisotropy
after laser heating. In an in-plane magnetized Pt/Co/Pt thin film with
perpendicular interface anisotropy, we found excellent agreement between
theoretical prediction with plausible parameters and experimental data measured
using time resolved magneto-optical Kerr effect. This agreement confirms that
the time evolution of the anisotropy field, which is driven by the interaction
between electrons and phonons, determines the magnetization precession
completely. A detailed analysis shows that, even though the whole sample is
magnetized in-plane, the dynamic interface anisotropy field dictates the
initial phase of the magnetization precession, highlighting the significance of
the interface anisotropy field in laser induced magnetization precession.Comment: 11 pages, 2 figure
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