Antiferromagnetic rare earth coupling in Pr_(1-x)Tb_xNi and Nd_(1-x)Tb_xNi single crystals

摘要

Magnetization and specific heat measurements were carried out on pseudo-binary Pr_(1-x)Tb_xNi (x = 0.0, 0.1) and Nd_(1-x)Tb_xNi (x=0.0, 0.05, 0.1, 0.15) single crystals. The magnetic transition temperatures for Pr_(1-x)Tb_xNi increased with x, whereas those for Nd_(1-x)Tb_xNi decreased slightly asx 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 Pr_(0.9)Tb_(0.1) Ni and indicates that there is a rearrangement of the magnetic moments. Calculations of the crystal electric field effect of Pr and Tb in Pr_(1-x)Tb_xNi were carried out using a simple point-charge model.