Structure and magnetic properties of off-stoichiometric Y2Co17 and Gd2Co17 compounds

Off-stoichiometric single-phase Gd2+xCo17−2x and Y2+xCo17−2x alloys were successfully prepared. For the Y2+xCo17−2x (x = 0-0.25) samples, the room temperature easy magnetization direction (EMD) is in the basal plane. For the Gd2Co17 compounds, the EMD at room temperature lies in the basal plane, whereas for the Gd2+xCo17−2x (x = 0.11) compound, the EMD lies on an easy-cone. With increasing x, the anisotropy fields of the Y2+xCo17−2x samples first increase quickly from 1.2 T for x = 0 to 1.4 T for x = 0.08, remain unchanged until x = 0.19, then decrease again to 1.1 T at x = 0.25. A spin-reorientation transition was found in the Gd2+xCo17−2x compounds, while there is no spin-reorientation for the Y2+xCo17−2x samples. The difference in anisotropy between the Gd2+xCo17−2x and Y2+xCo17−2x compounds was explained in terms of size effects, enthalpy effects and dipole-dipole interactions.