الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
We consider the Ising model in which the spins are coupled by infinite-ranged random interactions. These interactions are independently distributed with a Gaussian probability distribution. Both spin-glass (SG) and ferromagnetic (FM) systems occur. The competition between the spins and the type of the order parameter present in each are studied. An integral part of the development is the recognition that a new type of order parameter is necessary for the SG and plays a role even for more conventional phases in disordered systems. We calculated the free-energy (F), the susceptibility ( ), internal energy (U), the magnetization (m), and mean square of magnetization (q) by using mean field theory (MFT) in the presence of an external magnetic field. Extensive computer simulations of infinite-ranged Ising spin-glasses are presented. They confirm the general details of the predicted phase diagram. The errors in the replica solution are found to be small, and confined to low temperatures.
Finally, all the exact results obtained here for thermodynamic properties are compared with those of the earlier studies on the disordered magnetic systems. Our results are in complete agreement with many other Ising models in random field and spin glass systems and are in quantitative agreement with Monte Carlo studies.