Condensed Matter Physics, 2013, vol. 16, No. 2, p. 23007:1-9
DOI:10.5488/CMP.16.23007           arXiv:1307.2011

Title: Order parameter of a three-dimensional Ising-like system in the simplest and higher non-Gaussian approximations
  I.V. Pylyuk (Institute for Condensed Matter Physics of the National Academy of Sciences of Ukraine, 1 Svientsitskii St., 79011 Lviv, Ukraine)

The application of the collective variables method to the study of the behaviour of nonuniversal characteristics of the system in the critical region is illustrated by an example of the order parameter. Explicit expressions for the order parameter (the average spin moment) of a three-dimensional uniaxial magnet are obtained in approximations of quartic and sextic non-Gaussian fluctuation distributions (the ρ4 and ρ6 models, respectively), taking into account confluent corrections. Some distinctive features appearing in the process of calculating the order parameter on the basis of two successive non-Gaussian approximations are indicated. The dependence of the average spin moment of an Ising-like system on the temperature and microscopic parameters is studied.

Key words: three-dimensional Ising-like system, critical behaviour, non-Gaussian measure density, order parameter
PACS: 05.50.+q, 64.60.F-, 75.10.Hk

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