Dresden 2006 – scientific programme
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DY: Dynamik und Statistische Physik
DY 46: Poster
DY 46.122: Poster
Thursday, March 30, 2006, 16:00–18:00, P1
Effect of weak disorder on the ground state of uniaxial dipolar spin systems in the upper critical dimension — •A. V. Klopper1,2, U. K. Rößler2, and R.L. Stamps1 — 1School of Physics, University of Western Australia, Perth, Austalia — 2IFW Dresden, P.O. Box 270116, D-01171 Dresden, Germany
Extensive Monte Carlo simulations are used to investigate the
stability of the ferromagnetic ground state in 3D systems of Ising
dipoles with added quenched disorder modelled by short-range direct
+/−J exchange couplings. The uniaxial dipolar spins are arranged
on face centered cubic lattices with periodic boundary conditions.
These systems model the collective ferromagnetic order due to
classical dipole-dipole interactions observed in various
densely packed arrays of dipoles. Finite-size scaling relations for the
pure dipolar ferromagnetic system have been derived by a renormalization
group calculation. These functions include logarithmic corrections
to the expected mean field behaviour since the system is in its
upper critical dimension. Scaled data confirm the validity of the
finite-size scaling description and results are compared with
subsequent analysis of weakly disordered systems [1].
A disorder-temperature phase diagram displays the
preservation of the ferromagnetic ground state with the addition
of small amounts of disorder. Stronger disorder destroys the
ferromagnetic ground state. Different scenarios for the structure
of the phase diagram and the critical properties of disordered
systems are discussed.
[1] A.V. Klopper et al., cond-mat/0509751.