Antiferromagnetism and enhanced heat in CeM2Sn2 (M = Ni, Ir, Cu, Rh, Pd, and Pt).

摘要

Recently a new series of compounds has been discovered by M. Selsane et al. which has a structure close to CeCu2Si2. Specific heat, dc susceptibility, and resistivity measurements on annealed, polycrystalline samples of CeM2 Sn2 where M = Ni, Ir, Cu, Rh, Pd, or Pt indicate that each of these compounds orders antiferromagnetically with transition temperatures ranging from T(sub N) = 4.1 K to (approx) 0.5 K. All these materials have significant enhancements of the specific heat just before the transition which can be as large as (approximately)3.7 J/mole-K(sup 2) in some cases. Provided the enhanced heat capacities above T(sub N) are associated with large effective masses, the anomalously low ordering temperature and the very large C/T suggest that T(sub N) and the Kondo temperature T(sub K) are comparable, making these materials particularly attractive for studying the interplay between these competing interactions. In all cases except M = Ir, the susceptibility follows a Curie-Weiss behavior with a high temperature effective moment (mu)(sub eff) (approximately)2.54 (mu)(sub B)/Ce, while the Ir compound has a very strong mixed-valent nature. 14 refs., 3 figs., 2 tabs.