J-mixing effects on the anisotropy of Sm/sub 2/Co/sub 17/

Measurements of the temperature dependence of the anisotropy field H/sub A/ for Sm/sub 2/Co/sub 17/, Er/sub 2/Co/sub 17/, and Y/sub 2/Co/sub 17/ are reported. Two distinct values mere detected for the samarium compound at low temperature, as a result of the occurrence of in-plane magnetocrystalline anisotropy. From this data it was possible to derive the value of the sixth order anisotropy constant K/sub 3/'. However the crystal field model predicts zero value for the sixth-order anisotropy term if only the ground multiplet of the Sm/sup 3+/ ion is considered. This contradiction between theory and experiment was removed by taking into account the mixing of the lowest spin-orbit multiplets of Sm/sup 3+/ due to the exchange interaction. In this frame it was shown that a linear proportionality relation between K/sub 3/' and the sixth-order crystal field parameter B/sub 66/ is valid. This made possible a direct evaluation of B/sub 66/ from the experimental data. The influence of J mixing on the second-order anisotropy constant K/sub 1/ for Sm/sub 2/Co/sub 17/ and Er/sub 2/Co/sub 17/ was also investigated by analyzing the curve H/sub A/(T) in the temperature range T>200 K.