The anisotropy of Gd－Fe exchange interaction for Gd₂Fe₁₇ and Gd₂Fe₁₇H₃

The magnetization curves along the crystal axes for Gd_2Fe_17 and Gd_2Fe_17H_3 were analysed based on the single-ion model. If the Gd－Fe exchange interaction has been taken as isotropic as usual, the fitted values of magneto-crystalline anisotropy of the Fe sublattices in Gd_2Fe_17 and Gd_2Fe_17H_3 would become unreasonably different from those of the corresponding Y or Lu compounds. It was shown that the large difference is caused by the neglect of the anisotropy of the Gd－Fe exchange interaction.