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ISSN 2071-0186   Ukr. J. Phys. 2015, Vol. 60, N 4, p.362-370
doi:10.15407/ujpe60.04.0362    Paper

Kozlovskii M.P., Pylyuk I.V.

Institute for Condensed Matter Physics, Nat. Acad. of Sci. of Ukraine
(1, Svientsitskii Str., Lviv 79011, Ukraine; e-mail: piv@icmp.lviv.ua)

Analytical Description of the Critical Behavior of a Three-Dimensional Uniaxial Magnet in an External Field by Singling out a Reference System

Section: General problems of theoretical physics
Language: Ukrainian

Abstract: The critical behavior of systems belonging to the universality class of the three-dimensional Ising model has been studied theoretically. A three-dimensional Ising-like system with exponentially decreasing interaction potential and in the presence of a homogeneous external field was considered in the framework of the collective variables method. A specific feature in the calculation of the partition function and the free energy of a uniaxial magnet consists in singling out a reference system. The role of the latter is played by the molecular-field Hamiltonian. A method to describe the critical behavior with the use of a singled out reference system is developed on the basis of a non-Gaussian (quartic) distribution of order-parameter fluctuations (the 4 model).

Key words: Ising model, critical behavior, reference system, non-Gaussian distributions, free energy.