Evolution of the magnetic properties along the RCuBi₂ (R=Ce, Pr, Nd, Gd, Sm) series of intermetallic compounds

In this paper, the evolution of the magnetic properties along the series of intermetallic compounds RCuBi₂ (R=Ce, Pr, Nd, Gd, Sm) is discussed. These compounds crystallize in a tetragonal ZrCuSi₂ (P4/nmm) structure, and our single crystals of RCuBi₂ grown from Bi-flux show no evidence for Cu-deficiency [Ye et al., Acta Crystallogr. C 52, 1325 (1996)] as previously reported for R=Ce. For R=Ce, Pr, Gd, and Sm, we found an antiferromagnetic ordering at T_N ∼16K, 4.2K, 13.6K, and 4.9K, respectively. For R=Nd, we saw no evidence for a magnetic phase transition down to T=2K. These values of T_N clearly show a dramatic breakdown of the De Gennes factor in this series. We discuss our data taken into account the tetragonal crystalline electrical field and the anisotropic Ruderman-Kittel- Kasuya-Yoshida magnetic interaction between the R-ions in this family of compounds.