Degeneracy of antiferromagnetic Ising lattices at critical magnetic field and zero temperature

Abstract

The zero-point entropy and magnetization per site of the square and triangular Ising antiferromagnetic lattices in critical field have been calculated by a method that can be extended to three dimensions using a computer. The entropy for the triangular lattice is found to be $0.3333k\ensuremath{\approx}\frac{1}{3}k$ per site.