Cooperative magnetic behaviour in the new valence fluctuating compound Ce₂Rh₃Ge

Abstract

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 T(min)(χ(-1)) = 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.

Magnetoresistance of the CeCo1-xFexGe3 Alloys

“…For temperatures of 20 K and 30 K the isotherms show a smoother shaped curves with negative values in the whole magnetic field range. This a typical behavior of MR for a single-ion Kondo system, which is known for the Ce-based compounds [11,12]. Moreover, it suggests a magnetic phase transition around 10 K, which is in a good agreement with the presented resistivity results.…”

Magnetocrystalline anisotropy in the Kondo-lattice compound CeAgAs2

“…[100] and χ 0 = −4.797 × 10 −4 emu/mol, µ eff = 2.66 µ B /Ce Figure 2(b) shows the magnetic susceptibility for H [001] direction, which is very weak (of the order of 10 −3 emu/mol). It is obvious from the susceptibility data that the Curie-Weiss behaviour is absent and a broad hump is observed in the temperature range 50 to 300 K. This type of behaviour is usually attributed to mixed valent or intermediate valent character 16,28 . However, in the present case, we shall see that it arises due to a strong crystal field effect.…”

Field-insensitive heavy fermion features and phase transition in the caged-structure quasi-skutterudite Sm3 Ru4 Ge13

“…However a simple Curie-Weiss description was not suitable for Sm 3 Ru 4 Ge 13 and van Vleck terms in the total magnetic susceptibility were required to fit the data. The typical response of χ(T ) of compounds that displays valence fluctuation show a profound minimum which is due to the instability of 4 f shell and strong hybridization between the 4 f electron and conduction electron states [51]. The magnetic susceptibility of Sm 3 Ru 4 Ge 13 show a very weak variation of magnitude starting from 300 K toward 2 K. These features rule out the possibility of valence fluctuation though, mixed valence of Sm may be present.…”