Dresden 2006 – scientific programme
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DY: Dynamik und Statistische Physik
DY 44: Critical Phenomena and Phase Transitions III
DY 44.2: Talk
Thursday, March 30, 2006, 15:00–15:15, H\"UL 186
Anomalous superferromagnetic relaxation behavior in ordered magnetic structures — •Stefanie Russ and Armin Bunde — Institut für Theoretische Physik III, Universität Giessen, D-35392 Giessen
We perform Monte-Carlo simulations to study the anomalous magnetic relaxation behavior of single-domain ferromagnetic nanoparticles under the combined forces of diploar interaction and anisotropy effects, located at the sites of a simple cubic lattice. The anisotropy axes are orientated along the z-axes. We study how the system relaxes from two ordered states where all dipoles are orientated (a) along the antiferromagnetic ground-state and (b) along the z-direction of the lattice. We introduce appropriate order parameters O|| and O⊥ along the z-direction and in the xy-plane, respectively, to describe both, relaxation and final structure.
We find that below a critical temperature Tc, different structures are reached in both cases, which are described by the same value of O|| but by different values of O⊥. We discuss the possibility of obtaining a superferromagnetic state and compare the results with experiments on ultrafine magnetic particles.