Application of the Bethe-Peierls Method to a Metamagnetic, FeCl2

The magnetic properties of FeCl 2 , in which neutron diffraction experiments show that the metal atoms form ferromagnetic layers with alternate layers aligned antiparallel, are calculated using the Bethe-Peierls method. Account is taken of a ferromagnetic interaction of strength J F between nearest neighbours in a layer and an antiferromagnetic interaction of strength J A between next nearest neighbours in adjacent layers. Expressions are obtained for the usual thermodynamic functions as well as the critical scattering cross sections and are compared with experimental observations. The magnitudes of the interactions are found to be J F = 8.53 K , J A = 0.69 K , and with these values reasonable agreement is found between theory and experiment.