Statistical Mechanics of the Finite Heisenberg Model. III

概要

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The thermodynamic quantities of finite two- and three-dimensional ferromagnetic XY-model such as 3×3 and 2×2×2 lattices have been calculated for the purpose of investigating the properties of liquid Helium II. The density dependence of the λ-line for the finite quantum lattice gas model agrees with the results of molecular field approximation and the experimental data of pure He^4 liquid near the λ-transition. The possibility of the occurrence of negative thermal expansion coefficient below the λ-point was roughly discussed with the use of the same consideration as the Ising model of Lee and Yang. The magnetization versus field curve tends to a step function when the temperature becomes smaller than the critical temperature estimated from the maximum of the specific heat. There exists a great difference between the pure isotropic Heisenberg model and XY-model in the case of ferro-magnetic interaction at zero-temperature.
社団法人日本物理学会の論文
1970-06-05