Cooperative magnetic behaviour in the new valence fluctuating compound Ce₂Rh₃Ge

In this study we report the physical properties of the new ternary compound Ce₂Rh₃Ge that crystallizes in the rhombohedral, triple hexagonal MgCu₂-type of structure. The electronic ground state properties of Ce₂Rh₃Ge were characterized by magnetic susceptibility, specific heat, electrical resistivity and thermal transport measurements. The results indicate the presence of short range magnetic interaction, probably of ferromagnetic origin below T _C = 4 K. The shape of χ ^-1(T) deviates from the Curie-Weiss behavior with a broad minimum at about = 450 K reminiscent of valence fluctuating cerium systems. At T = 10 K, the magnetic part of the resistivity ρ _{4 f}(T) exhibits a shallow minimum followed by increase of resistivity ρ(T) -lnT, which hints at a substantial Kondo screening effect. Ce₂Rh₃Ge belongs to a small group of strongly correlated cerium compounds in which the two competing effects of Kondo and RKKY interactions produce long-range magnetic order from strongly hybridized and intermediate-valent 4 f spins. At sufficiently low temperatures Ce₂Rh₃Ge scales well with the Kadowaki-Woods ratio A/γ ² and the value of the Wilson ratio χ(T → 0)/γ found for this compound classifies it as a mixed-valence compound. The presence of valence fluctuation and magnetic order it is rare for these attributes to be found simultaneously in same compound, in same temperature range. In our opinion a novelty of presented results of Ce₂Rh₃Ge is that this compound adds a new member to a small but growing class of systems bearing a strongly mixed- or intermediate-valent 4 f magnetic moment, but in which the lattice of spins nevertheless end up finding it possible to order magnetically.