Regensburg 2010 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 27: Spin Structures and Magnetic Phase Transitions
MA 27.4: Vortrag
Donnerstag, 25. März 2010, 18:00–18:15, H10
Low-energy excitations in the three-dimensional random-field Ising model — Martin Zumsande1,2 and •Alexander K. Hartmann3 — 1Institute of Theoretical Physics, University of Göttingen — 2Max-Planck Institut fof Physics of Complex Systems, Dresden — 3Institute of Physics, University of Oldenburg
The random-field Ising model (RFIM), one of the basic models for magnetic alloys exhibiting quenched disorder, can be studied numerically [1] with the help of efficient ground-state algorithms [2]. In this study [3], we extend these algorithm by various methods in order to analyze low-energy excitations for the three-dimensional RFIM with Gaussian distributed disorder as a function of the disordered strength, i.e. in the ferromagnetic phase, in the paramagnetic phase and right at the phase transition. These excitations appear in the form of clusters of connected spins. We analyze several properties of these clusters. Also we show that the stiffness exponent θ, describing the scaling of the energy of the excitations, is related to the distribution of cluster radii via P(R)∼ R−θ. Our results support the validity of the droplet-model description for the RFIM.
[1] A.K. Hartmann, Practical Guide to Computer Simulations, (World Scientific, 2009)
[2] A.K. Hartmann and Heiko Rieger, Optimization Algorithms in Physics, (Wiley-VCH, 2001)
[3] M. Zumsande and A.K. Hartmann, to appear in Eur. Phys. J. B