J-mixing effects on the anisotropy of Sm2Co17

Measurements of the temperature dependence of the anisotropy field H-A for Sm2Co17, Er2Co17, and Y2Co17 are reported. Two distinct values were detecte d for the samarium compound at low temperature, as a result of the occurren ce of in-plane magnetocrystalline anisotropy. From this data it was possibl e to derive the value of the sixth order anisotropy constant K-3'. However the crystal field model predicts zero value for the sixth-order anisotropy term if only the ground multiplet of the Sm3+ ion is considered. This contr adiction between theory and experiment was removed by taking into account t he mixing of the lowest spin-orbit multiplets of Sm3+ due to the exchange i nteraction. In this frame it was shown that a linear proportionality relati on between K-3' and the sixth-order crystal field parameter B-66 is valid. This made possible a direct evaluation of B-66, from the experimental data. The influence of J mixing on the second-order anisotropy constant K-1 for Sm-2 Co-17 and Er2Co17 was also investigated by analyzing the curve H-A(T) in the temperature range T > 200 K.