Crystal structure and magnetic properties of mixed compounds Nd_1–xR_xCo₃ (R = Gd, Tb)

The crystal structure and magnetic properties of Nd_1–xR_xCo₃ (R = Gd, Tb) have been investigated by means of X-ray powder diffraction and magnetic measurements. Spin reorientation and magnetization compensation are observed in both systems. The saturation magnetization M_S of Nd_1–xTb_xCo₃ exhibits an anomaly at a critical concentration x_c ≈ 0.55, whereas no such an anomaly is observed for Nd_1–xGd_xCo₃. These observations could be understood by considering the difference of the anisotropy between Tb³⁺ and Gd³⁺ ions. The type of magnetocrystalline anisotropy of the compounds is derived based on X-ray diffraction patterns of the field-aligned samples. For Nd_1–xTb_xCo₃, the anisotropy near x_c is weak with an undefined easy magnetization direction. On the Nd-rich side, the anisotropy exhibits a strong temperature dependence. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)