LOW-TEMPERATURE BEHAVIOR OF 2 TERNARY LANTHANIDE NICKEL CARBIDES - SUPERCONDUCTING LANIC2 AND MAGNETIC CENIC2

A study of the magnetic properties and the heat capacity as functions of temperature and magnetic field of two ternary carbides RNiC2, where R = La and Ce, confirms that LaNiC2 becomes superconducting at T-c = 2.7 K, and that CeNiC2 orders antiferromagnetically below 18 K. LaNiC2 is a conventional superconductor with a critical field of 900 Oe at T = 2 K. CeNiC2 obeys the Curie-Weiss law between 50 and 300 K showing the nearly full Ce3+ magnetic moment, p(eff) = 2.47(1)mu(B), and has a negative paramagnetic Weiss temperature Theta(p) = -18.3(8) K. A low net magnetic moment in the ordered state, which is far from saturation in a magnetic field of 5 T, is consistent with an antiferromagnetic g round state. Below 20 K CeNiC2 shows multiple-step magnetic transition s at 18, 10, and 2.4 K. Both LaNiC2 (in the normal state) and CeNiC2 h ave the same electronic heat capacity, gamma = 6.5(2) mJ/mol K-2, whic h is typical for many lanthanide-based intermetallic compounds. The De bye temperature of LaNiC2 determined from the heat capacity in the nor mal state below 5.5 K is Theta(D) = 388(9) K. [S0163-1829(98)06425-X].