Study of the critical behaviour of three-dimensional Ising-like systems on the basis of theρ6model with allowance for microscopic parameters: I. High-temperatureregion

Abstract

The behaviour of a three-dimensional Ising-like system at temperatures above the criticalvalue of Tc isstudied in the approximation of the sextic distribution for modes of spin density oscillations(ρ6model). The original collective variables method is developed in this higher non-Gaussianapproximation for calculating the thermodynamic characteristics of the system nearTctaking into account the first confluent correction. The calculations are illustratedby an example of a simple cubic lattice and an exponentially decreasinginteraction potential. The main distinctive feature of the method is theseparate inclusion of the contributions to the thermodynamic functionsfrom the short-wave and long-wave spin density oscillation modes. Thedependences of the phase transition temperature, leading critical amplitudes, andcorrection-to-scaling amplitudes for the specific heat and susceptibility on themicroscopic parameters of the system are investigated.