No abstract

The diluted mixed spin Ising system consisting of spin-1/2 and spin-1 with a random field is studied by the use of the finite cluster approximation within the framework of a single-site cluster theory. The state equations are derived using a probability distribution method based on the use of Van der Waerden identities. In this approach, the complete phase diagrams are investigated for the simple cubic lattice, when the random field is bimodally and trimodally distributed. The internal energy, specific heat and susceptibility are also calculated for both kinds of probability distributions.

PACS 75.10.Hk, 75.50.Gg The phase diagram of the three-dimensional transverse Ising system with competing surface and bulk exchange interactions is studied by the use of an effective-field method within the framework of a single-site cluster theory. In addition to this pure case, which shows qualitatively interesting features, we investigated the effects of the bond dilution on the obtained phase diagram. In particular, we studied the influence of the surface dilution parameter on the surface transitions. We find a number of characteristic behaviours of the surface both in the absence and in the presence of the surface transverse field.

No abstract