Magnetism and spin fluctuation effects in heavy-fermion CeRu₂Si₂ induced by partial substitution of Ru and Si

Abstract

The effect of chemical substitution in CeRu₂Si₂, a well-studied heavy-fermion system, has been investigated through magnetic susceptibility and x-ray diffraction measurements in the systems CeRu_xSi₂, CeRu_2-xOs_xSi₂, CeRu₂Si_2-xC_x, and CeRu₂Si_2-xGe_x. Replacing silicon by carbon and germanium generates the normal chemical-pressure effect, namely Ce atoms in CeRu₂Si_2-xC_x and CeRu₂Si_2-xGe_x are, respectively, less and more magnetic than in CeRu₂Si₂. With increasing Ge concentration, CeRu₂Si_2-xGe_x first exhibits a larger low-temperature susceptibility than that in pure CeRu₂Si₂, then goes into an antiferromagnetic phase, and finally becomes ferromagnetic. Electronic effects are more important than the chemical-pressure effect in CeRu_2-xOs_xSi₂ since the lattice constants of CeOs₂Si₂ are very nearly the same as those of CeRu₂Si₂. It is conjectured that CeRu₂Si_2-xGe_x may be the first Ce-based heavy-fermion system having a magnetic ground state.