Influence of Al substitution on the structure and Co-sublattice magnetocrystalline anisotropy of Gd2Co17 compounds

The structure and magnetic properties of ${\mathrm{Gd}}_2{\mathrm{Co}}_{\text{17−x}}{\mathrm{Al}}_x$ compounds were investigated. All samples have a rhombohedral ${\mathrm{Th}}_2{\mathrm{Zn}}_{17}$ -type structure and the replacement of Co by Al results in an approximately linear increase in the unit cell volumes at a rate of 8.2 ${\AA }^3$ /Al. The Curie temperature decreases monotically with the increase of Al concentration. On the basis of magnetization curves at the compensation temperature, the intersublattice-molecular-field coefficient, $n_{\mathrm{RT}},$ and the RT exchange-coupling constant $J_{\mathrm{RT}}$ have been determined. It is noteworthy that the substitution of Al has a significant effect on the magnetocrystalline anisotropy of the Co sublattice, and changes the easy magnetization direction of ${\mathrm{Gd}}_2{\mathrm{Co}}_{\text{17−x}}{\mathrm{Al}}_x$ compounds from the basal plane to the $c$ axis.