Mean-field transfer-matrix study of the magnetic phase diagram of   CsNiF$_{\bf 3}$
  A method for treating ferromagnetic chains coupled with antiferromagnetic interactions on an hexagonal lattice is presented in this paper. The solution of the $1D$ part of the problem is obtained by classical transfer-matrix while the coupling between the chains is processed by mean-field theory. This method is applied with success to the phase diagram and angular dependence of the critical field of CsNiF$_3$. Results concerning the general influence of single-ion anisotropy on the magnetic ordering of such systems are also presented. 
Y. Trudeau, M. L. Plumer (Centre de Recherche en Physique du Solide et   D\'epartement de Physique Universit\'e de Sherbrook...