On the structural and magnetic properties of the ternary silicides Ce 6M1.67Si 3 ( M=Co, Ni) and Ce 5Ni 1.85Si 3

Abstract

Contrary to that reported previously, the ternary silicide “Ce 6Ni 2Si 3” does not exist. The melting of this alloy, followed or not by annealing, leads to the existence of the two new ternary compounds, Ce 6Ni 1.67Si 3 and Ce 5Ni 1.85Si 3. The investigation of these ternary silicides based on nickel and Ce 6Co 1.67Si 3 by X-ray diffraction on single crystal reveals an ordered distribution between Ni (or Co) and Si atoms. The nickel or cobalt positions in the chains of face-shared octahedra of cerium are not fully occupied with a strong delocalisation of their electron density. The structural investigations of these compounds confirm that the “Ce 6Ni 2Si 3” and “Ce 5Ni 2Si 3” structural type have to be rewritten as Ce 6Ni 2− x Si 3 and Ce 5Ni 2− x Si 3. Magnetisation and specific heat measurements evidence a magnetic ordering at 3.8(2) K for Ce 6Ni 1.67Si 3 and a heavy fermion behaviour for Ce 6Co 1.67Si 3.