Valence fluctuations in Ce2Rh3+xGe1-x

Ternary intermetallic alloys Ce2Rh3+xGe1-x (0 ≤ x ≤ 0.33) have been found to crystallize in a rhombohedral structure of the Mg2Ni3Si-type (space group R-3m). With varying the stoichiometry, the lattice parameters significantly vary from a = 5.5887(2) Å, c = 11.9557(5) Å (hexagonal setting) for x = 0 to a = 5.5127(2) Å, c = 12.2790(5) Å for x = 0.33, while the unit cell volume remains nearly unchanged. By means of magnetic susceptibility, heat capacity and electrical resistivity measurements, the Ce2Rh3+xGe1-x alloys have been shown to be intermediate valence systems with highly unstable 4f shell of Ce ions. Notably, the ferromagnetic ordering, claimed in the literature to coexist with the valence fluctuations in Ce2Rh3Ge, has been revealed to be an extrinsic effect due to impurity contribution.