5,162 research outputs found
Micromagnetic simulations of interacting dipoles on a fcc lattice: Application to nanoparticle assemblies
Micromagnetic simulations are used to examine the effects of cubic and axial
anisotropy, magnetostatic interactions and temperature on M-H loops for a
collection of magnetic dipoles on fcc and sc lattices. We employ a simple model
of interacting dipoles that represent single-domain particles in an attempt to
explain recent experimental data on ordered arrays of magnetoferritin
nanoparticles that demonstrate the crucial role of interactions between
particles in a fcc lattice. Significant agreement between the simulation and
experimental results is achieved, and the impact of intra-particle degrees of
freedom and surface effects on thermal fluctuations are investigated.Comment: 10 pages, 9 figure
Damage spreading in two dimensional geometrically frustrated lattices: the triangular and kagome anistropic Heisenberg model
The technique of damage spreading is used to study the phase diagram of the
easy axis anisotropic Heisenberg antiferromagnet on two geometrically
frustrated lattices. The triangular and kagome systems are built up from
triangular units that either share edges or corners respectively. The
triangular lattice undergoes two sequential Kosterlitz-Thouless transitions
while the kagome lattice undergoes a glassy transition. In both cases, the
phase boundaries obtained using damage spreading are in good agreement with
those obtained from equilibrium Monte Carlo simulations.Comment: 7 pages, 4 figure
Absence of aging in the remanent magnetization in Migdal-Kadanoff spin glasses
We study the non-equilibrium behavior of three-dimensional spin glasses in
the Migdal-Kadanoff approximation, that is on a hierarchical lattice. In this
approximation the model has an unique ground state and equilibrium properties
correctly described by the droplet model. Extensive numerical simulations show
that this model lacks aging in the remanent magnetization as well as a maximum
in the magnetic viscosity in disagreement with experiments as well as with
numerical studies of the Edwards-Anderson model. This result strongly limits
the validity of the droplet model (at least in its simplest form) as a good
model for real spin glasses.Comment: 4 pages and 3 figures. References update
Monte Carlo simulations of magnetic ordering in the fcc Kagome lattice
Monte Carlo simulation results are reported on magnetic ordering in ABC
stacked Kagom\'{e} layers with fcc symmetry for both XY and Heisenberg models
which include exchange interactions with the eight near-neighbors. Well known
degeneracies of the 2D system persist in the 3D case and analysis of the
numerical data provides strong evidence for a fluctuation-driven first-order
transition to well-defined long-range order characterized as the layered
(120-degree) spin structure. Effects of varying the inter-layer coupling are
also examined. The results are relevant to understanding the role of
frustration in IrMn alloys widely used by the magnetic storage industry as
thin-films in the antiferromagnetic pinning layer in GMR and TMR spin valves.
Despite the technological importance of this structure, it has not previously
been noted that the magnetic Mn-ions of fcc IrMn form Kagom\'{e} layers.Comment: 9 pages, 14 figures. Submitted to Phys. Rev.
Spin Stiffness of Stacked Triangular Antiferromagnets
We study the spin stiffness of stacked triangular antiferromagnets using both
heat bath and broad histogram Monte Carlo methods. Our results are consistent
with a continuous transition belonging to the chiral universality class first
proposed by Kawamura.Comment: 5 pages, 7 figure
- …