Ising spins spin glass models

This nanoparticle sample exhibits strong anisotropy, due to the uniaxial anisotropy of the individual particles and the anisotropic dipolar interaction. The relative timescales (f/xm) of the experiments on nanoparticle systems are shorter than for conventional spin glasses, due to the larger microscopic flip time. The nonequilibrium phenomena observed here are indeed rather similar to those observed in numerical simulations on the Ising EA model [125,126], which are made on much shorter time (length) scales than experiments on ordinary spin glasses [127]. 

F. Barahona (1982) On the computational complexity of Ising spin glass models. J. Phys. A 15, p. 3241... 

Extensive studies of the 2-dimensional EA-Ising model with Gaussian distributed nearest neighbor bonds by Monte Carlo simulations (Binder and Schroder 1976, Kinzel 1979, Kinzel and Binder 1984) provide evidence that the EA model reproduces many experimental findings on real spin glasses remarkably well. For instance... 

Fig. 18. Magnetic phase diagram for the SK model (EA model for Ising spins with infinite-range couplings). J and / denote the width and mean of the exchange distribution. P = paramagnet FM = ferromagnet SG = spin glass. F is a ferromagnetic phase viith replica symmetry breaking, i.e. irreversibility ( mixed phase ) and is separated from FM by an AT line.

The first question has been studied by computer simulations (Kinzel and Binder 1984). Even the two-dimensional EA-Ising model with a Gaussian distribution of nearest-neighbor interactions reproduces several experiments described above qualitatively in surprising many details (see also sec. 4.2). Since this 2D-model has a spin-glass transition at = 0, the = 0-hypothesis (Binder and Young 1984)... 

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