ANTIFERROMAGNETISM AND ENHANCED SPECIFIC-HEAT IN CEM2SN2 (M = NI, IR, CU, RH, PD AND PT)

Specific heat, DC susceptibility, and resistivity measurements on annealed, polycrystalline samples of CeM2Sn2, where M = Ni, Ir, Cu, Rh, Pd, or Pt, indicate that each of these compounds orders antiferromagnetically with transition temperatures ranging from T(N) = 4.1 to almost-equal-to 0.5 K. All these materials have significant enhancements of the specific heat just before the transition, which can be as large as approximately 3.5 J/mol K2 in some cases. Provided the enhanced heat capacities above T(N) are associated with large effective masses, the anomalously low ordering temperature and the very large C/T suggest that T(N) and the Kondo temperature T(K) are comparable, making these materials particularly attractive for studying the interplay between these competing interactions. The susceptibility for each member of the series except M = Ir follows a Curie-Weiss behavior with a high-temperature effective moment mu-eff approximately 2.5-mu-B/Ce and a small negative paramagnetic Curie temperature.