Magnetic properties of the tetragonal compounds CeB2C2 and PrB2C2

Abstract Magnetic properties of CeB2C2 and PrB2C2 compounds have been investigated by means of magnetization, specific heat and elastic constant measurements on single-crystalline samples. CeB2C2 is an antiferromagnet of TN=7.3 K with a moment direction in the tetragonal [0 0 1]-plane. An order–order transition appears at 6.5 K, which is observed in the specific heat and the anomaly in the susceptibility is extremely small. The magnetization measurement confirms that PrB2C2 is a Van Vleck paramagnet. The 4f ground state of PrB2C2 is a singlet with a magnetic doublet as a first excited state. The analyses based on the second-order approximation of crystalline electric field (CEF) interaction give no systematic result. The second-order CEF parameter A20 is positive in PrB2C2, although that is negative in CeB2C2 which is similar to that in NdB2C2. It is supposed that the CEF interactions of higher order play important roles in the RB2C2 system.