A comparative study of magnetic behaviors in TbNi₂, TbMn₂ and TbNi₂Mn

All TbNi₂, TbMn₂, and TbNi₂Mn compounds exhibit the cubic Laves phase with AB₂-type structure in spite of the fact that the ratio of the Tb to transition-metal components in TbNi₂Mn is 1:3. Rietveld refinement indicates that in TbNi₂Mn the Mn atoms are distributed on both the A (8a) and B (16d) sites. The values of the lattice constants were measured to be a = 14.348 Å (space group F-43 m), 7.618 Å, and 7.158 Å (space group Fd-3 m) for TbNi₂, TbMn₂, and TbNi₂Mn, respectively. The magnetic transition temperatures T_C were found to be T_C = 38 K and T_C = 148 K for TbNi₂ and TbNi₂Mn, respectively, while two magnetic phase transitions are detected for TbMn₂ at T₁ = 20 K and T₂ = 49 K. Clear magnetic history effects in a low magnetic field are observed in TbMn₂ and TbNi₂Mn. The magnetic entropy changes have been obtained.