Spin fluctuation effects in substituted CeRu₂Si₂ and YbPd₂Si₂ alloys

Abstract

Effects of chemical substitution in CeRu₂Si₂, a well-studied heavy fermion system and YbPd₂Si₂ have been investigated through magnetic susceptibility and X-ray diffraction in the systems CeRu_xSi₂, CeRu_2−xOs_xSi₂, CeRu₂Si_2−x Ge_x and YbPd₂Si_2−x Ge_x. Replacing silicon by germanium generates normal chemical pressure effect, namely, Ce and Yb atoms in CeRu₂Si₂ and YbPd₂Si₂ became more and less magnetic respectively. With increasing Ge concentration, CeRu₂Si_2−x Ge_x exhibits larger susceptibility at low temperature, goes to an antiferromagnetic state and finally becomes ferromagnetic. In YbPd₂Si_2−xGe_x , increasing Ge concentration drives Yb atoms to more divalent state. Electronic effects are more pronounced in CeRu_2−xOs_x Si₂ though CeRu₂Si₂ and CeOs₂Si₂ have very nearly the same lattice parameters. It is conjectured that CeRu₂Si_2−xGe_x may be the first Ce-based heavy fermion having a magnetic ground state.