Crossing-over from the 2d-Ising to the 2d-Heisenberg System

Abstract

Based on the present theoretical status of the phase transition of the 2d-Heisenberg system, we re-examined in the anisotropic 2d-Heisenberg system the crossing-over from the 2d-Ising to the 2d-Heisenberg class for the amplitude of the specific heat capacity and the coefficient of the inverse correlation length in terms of the weak universality. It is clarified that in the anisotropy region Δ=0.002∼1 the system follows the strong universality. However, near Δ=0 the system should follow the weak universality in connection with the characteristic behavior of the temperature dependence of the correlation length in the 2d-Heisenberg system.