Antiferromagnetic rare earth coupling in Pr1−xTbxNi and Nd1−xTbxNi single crystals

Magnetization and specific heat measurements were carried out on pseudo-binary Pr1−xTbxNi (x = 0.0, 0.1) and Nd1−xTbxNi (x = 0.0, 0.05, 0.1, 0.15) single crystals. The magnetic transition temperatures for Pr1−xTbxNi increased with x, whereas those for Nd1−xTbxNi decreased slightly as x increased. The effective magnetic moments, deduced from the temperature dependence of susceptibility, increased with x for both systems. The saturation magnetizations observed at the magnetically easy directions for all samples suggest that the magnetic coupling between the Pr (or Nd) and Tb moments is antiferromagnetic. A noticeable increase in magnetization in higher external field, onset at 5 T, is observed for Pr0.9Tb0.1Ni and indicates that there is a rearrangement of the magnetic moments. Calculations of the crystal electric field effect of Pr and Tb in Pr1−xTbxNi were carried out using a simple point-charge model.