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DY: Dynamik und Statistische Physik

DY 46: Poster

DY 46.123: Poster

Donnerstag, 30. März 2006, 16:00–18:00, P1

Phase diagrams of the mixed-spin Ising model on the decorated square lattice — •Jozef Strecka, Lucia Canova, and Jan Dely — Department of Theoretical Physics and Astrophysics, Faculty of Science, P. J. Safarik University, 040 01 Kosice, Slovakia

Generalized version of decoration-iteration transformation is used in order to establish a mapping correspondence between the mixed-spin Ising model on the decorated square lattice and respectively, a simple spin-1/2 Ising model on the anisotropic square lattice solved by Onsager several years ago [1]. Even if horizontal bonds of the decorated square lattice are occupied by different spins as the vertical ones, this mapping procedure enables to obtain exact results for phase diagrams as well as all basic thermodynamic quantities such as Gibbs free energy, magnetization, specific heat, etc.

Within the framework of this mapping, we will investigate in particular the phase diagrams depending basically on the single-ion anisotropy strength acting on the higher-spin sites. It turns out that the system under investigation may exhibit very rich and unexpected critical behaviour, which strongly depends on the spin quantum number of decorating sites. In addition, a detailed analysis of the temperature dependence of the total magnetization will be accomplished for the ferrimagnetic version of the model system, since the ferrimagnetic spin systems often exhibit manifold temperature dependences of the total magnetization.

[1] L. Onsager, Phys. Rev. 65 (1944) 117.