CALORIMETRIC STUDY OF THE CRYSTAL-FIELD AND EXCHANGE INTERACTIONS IN NDNI2, TBNI2, AND DYNI2

The heat capacity of the intermetallic compounds NdNi2, TbNi2, and DyN i2 have been measured from 2 to 300 K with ac calorimetry. Magnetic or dering is observed at 10.2, 33.0 and 18.6 K, respectively. The three c ompounds also show Schottky anomalies around 50 K coming from low ener gy levels of the rare-earth ion. The magnetic heat capacity has been d escribed with a simple model taking into account the energy splitting of the ground multiplet due to the crystalline electric field (CEF) an d the exchange interaction in a molecular-field approximation. The cry stal-field and exchange parameters have been deduced from our experime ntal results and compared with values previously reported.