STUDY OF RE IRON GARNETS USING A MODIFIED BPW METHOD

We present the results of a study of the magnetic susceptibility of ra n-earth iron garnets, R(3)Fe(5)O(12), with R = Gd, Tb, Dy, Ho, Er and Yb, using a modified Bethe-Peierls-Weiss (BPW) approximation. The modi fications enable us to incorporate the six exchange integral constants necessary to describe three-sublattice systems. We have obtained exce llent fits to the experimental susceptibilities, from which we determi ned the exchange constants as parameters. For the case of gadolinium g arnets, we have also obtained the spin wave dispersion relation consta nt D, in excellent agreement with the value obtained from an analysis of the experimental low-temperature specific heat data.