Phase formation and ground state properties ofCeCo9Si4

Abstract

The phase relations of the CeCo9 + δSi4 − δ system have been studied by means of scanning electron microscopy, electronmicroprobe analysis and x-ray diffraction. Essentially single phase samplesCeCo9 + δSi4 − δ (structure-typeLaFe9Si4 with spacegroup I4/mcm) are formed in a narrow composition range − 0.3 ≤ δ < 0.1, wherestoichiometric CeCo9Si4 exhibits full structural order in space groupI4/mcm. The evolution of the ground state of correlated 3d and 4f electrons in the solid solutionCeCo9 + δSi4 − δ has beeninvestigated by dc susceptibility, magnetization, specific heat and resistivity measurements. StoichiometricCeCo9Si4 exhibits paramagnetic Kondo lattice behaviour with a largely reduced Co 3dcontribution to the magnetic susceptibility as compared to nearly ferromagneticLaCo9Si4. Nonetheless, very similar to the solid solutionLaCo9 + δSi4 − δ, weak ferromagnetismis observed in CeCo9 + δSi4 − δ for δ > 0 and is attributed to substitutional disorder at the Si-sublattice.