Magnetic properties of the tetragonal compounds CeB2C2 and PrB2C2

Magnetic properties of CeB2C2 and PrB2C2 compounds have been investigated b y means of magnetization, specific heat and elastic constant measurements o n single-crystalline samples. CeB2C2 is an antiferromagnet of T-N = 7.3 K w ith a moment direction in the tetragonal [001]-plane. An order-order transi tion appears at 6.5 K, which is observed in the specific heat and the anoma ly in the susceptibility is extremely small. The magnetization measurement confirms that PrB2C2 is a Van Vleck paramagnet. The 4f ground state of PrB2 C2 is a singlet with a magnetic doublet as a first excited state. The analy ses based on the second-order approximation of crystalline electric field ( CEF) interaction give no systematic result. The second-order CEF parameter A(2)(0) 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 hig her order play important roles in the RB2C2 system. (C) 2000 Elsevier Scien ce B.V. All rights reserved.