Spin Correlations and Magnetic Susceptibility of the Two-Dimensional Ising Model

Abstract

For the Ising model on the two-dimensional lattice withM× N spin sites (M is a finite number; N→ ∞), arbitrary two-spin correlations are evaluated exactly. We make use ofspinor analysis, which was employed by Kaufman and Onsager. Thezero-field magnetic susceptibility χ₀ that is equal to the sumof all two-spin correlations, is calculated.