Induced 3d and 4f magnetism in Gd_1-xPr_xNi₂ Laves phase alloys

The series of Gd_1-xPr_xNi₂ (x = 0.25, 0.40, and 0.60) polycrystalline samples has been investigated using x-ray diffraction and magnetometry. The x-ray diffraction measurements showed that the lattice constant and the relative intensities of the C15 superstructure I ₅₁₁/I₄₄₀ and I₅₁₁/I₂₂₀ increase with the praseodymium content, reflecting an increasing number of ordered vacancies at the 4a sites. The temperature dependences of the zero-field cooled (M _ZFC(T)) and field cooled (M_FC(T)) magnetizations show that a moment is induced by the gadolinium on the Pr³⁺ ion and on the nickel subsystem. In the ordered phase both induced moments are antiparallel to that of the Gd³⁺ ion. A cusp is observed at a temperature T _max in the M_ZFC(T) curve. Both critical temperatures T_c and T_max are found to decrease with increasing praseodymium content, indicating a reduction in strength of the antiparallel coupling for Gd-Pr and Gd-Ni pairs.