A Theory of Antiferromagnetism, II

Abstract

General theories of ferromagnetism and antiferromagnetism based on the Heisenberg model are given in this paper, which are extensions of the Weiss theory. The approximation of these theories is not so good as that of our previous theories, but the main object of this paper is to develop simple and tractable theories which can include the short range order effects. The perpendicular susceptibility of antiferromagnet below the Néel point is obtained, which is almost independent of temperature. The large residual entropy above the Néel point of CuCl2-2H2O can be explained by application of the present theory.