Calorimetric study of the crystal-field and exchange interactions in NdNi2, TbNi2, and DyNi2

The heat capacity of the intermetallic compounds NdNi2, TbNi2, and DyNi2 have been measured from 2 to 300 K with ac calorimetry. Magnetic ordering is observed at 10.2, 33.0 and 18.6 K, respectively. The three compounds also show Schottky anomalies around 50 K coming from low energy levels of the rare-earth ion. The magnetic heat capacity has been described with a simple model taking into account the energy splitting of the ground multiplet due to the crystalline electric field (CEF) and the exchange interaction in a molecular-field approximation. The crystal-field and exchange parameters have been deduced from our experimental results and compared with values previously reported.