Abstract
In this work, we study the dynamic critical behavior of the
three-dimensional Heisenberg (HM) and double-exchange (DEM) models
through short-time Monte Carlo simulations
Fernandes2005,Fernandes2006a,Fernandes2006b. The hamiltonian
of the models are given, respectively, by
eqnarray*
H_HM=-J\sum_i,jS_i\cdot
S_j
eqnarray*
and
eqnarray*
H_DEM=-J\sum_łangle
i,j1+\mathbfS_iS_j
eqnarray*
where $J>0$ is the ferromagnetic coupling constant,
$S_i=(S_i^x,S_i^y,S_i^z)$ is a
three-dimensional vector of unit length, located on each site of a
simple cubic lattice, and $i,j$ indicates that the
sum runs over the pairs of nearest-neighbors of the lattice sites.
The dynamic critical exponents $z$, $þeta$, and $þeta_g$, as
well as, the static critical exponents $\nu$ and $\beta$ were
estimated by following the time evolution of the total magnetization
and its moments of higher order. The anomalous dimension of the
magnetization $x_0$ was obtained through the scaling relation
$x_0=z + \beta/\nu$ which is found in systems
out-of-equilibrium. Our estimates for $z$, $\nu$, and $\beta$, for
both models, are in good agreement with each other and with values
found in the literature. The exponents $þeta$ and $þeta_g$ for
the Heisenberg and double-exchange models are in complete agreement
with each other, asserting once more the idea which both models
belong to the same universality class. To our knowledge, this is the
first time that the exponents $þeta$ and $þeta_g$ are calculated
for three-dimensional models with continuous spin variables.\\
H.A. Fernandes, J.R. Drugowich de Fel\'ıcio, and
A.A. Caparica, Short-time behavior of a classical
ferromagnet with double-exchange interaction, Phys. Rev. B.
72, 054434 (2005).\\
H. A. Fernandes and J. R. Drugowich de
Fel\'ıcio, Global persistence exponent of the
double-exchange model, Phys. Rev. E 73, 57101 (2006).\\
H. A. Fernandes, Roberto da Silva, and J. R.
Drugowich de Fel\'ıcio, Short-time critical and
coarsening dynamics of the classical three-dimensional Heisenberg
model, J. Stat. Mech.: Theor. Exp., P10002 (2006).
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