Valence fluctuations in Ce2Rh3+xGe1-x

Ternary intermetallic alloys Ce 2 Rh 3+x Ge 1-x (0 ≤ x ≤ 0.33) have been found to crystallize in a rhombohedral structure of the Mg 2 Ni 3 Si-type (space group R -3 m ). With varying the stoichiometry, the lattice parameters significantly vary from a = 5.5887(2) A, c = 11.9557(5) A (hexagonal setting) for x = 0 to a = 5.5127(2) A, c = 12.2790(5) A for x = 0.33, while the unit cell volume remains nearly unchanged. By means of magnetic susceptibility, heat capacity and electrical resistivity measurements, the Ce 2 Rh 3+x Ge 1-x alloys have been shown to be intermediate valence systems with highly unstable 4 f shell of Ce ions. Notably, the ferromagnetic ordering, claimed in the literature to coexist with the valence fluctuations in Ce 2 Rh 3 Ge, has been revealed to be an extrinsic effect due to impurity contribution.