Superconducting phase transition in YNiGe3, a non-f-electron reference to the unconventional superconductor CeNiGe3

A polycrystalline sample of YNiGe3, being a non-magnetic isostructural counterpart to the unconventional pressure-induced superconductor CeNiGe3, was studied by means of specific heat and electrical resistivity measurements at temperatures down to 360 mK and in magnetic fields up to 500 Oe. The compound was found to exhibit an ambient-pressure superconductivity below Tc = 0.46 K. The superconducting state in YNiGe3 is destroyed by magnetic field of the order of 500 Oe.Comment: to appear in Solid State Communication

Single-ion Kondo Scaling of the Coherent Fermi Liquid Regime in Ce1-xLaxNi2Ge2

Thermodynamic and transport properties of the La-diluted Kondo lattice CeNi2Ge2 were studied in a wide temperature range. The Ce-rich alloys Ce1-xLaxNi2Ge2 were found to exhibit distinct features of the coherent heavy Fermi liquid. At intermediate compositions (0.7 <= x <= 0.9) non-Fermi liquid properties have been observed, followed by the local Fermi liquid behavior in the dilute limit. The 4f-electron contribution to the specific heat was found to follow the predictions of the Kondo impurity model both in the local as well as coherent regimes, with the characteristic Kondo temperature decreasing rapidly from about 30 K for the parent compound CeNi2Ge2 to about 1K in the most dilute samples. The specific heat does not show any evidence for the emergence of a new characteristic energy scale related to the formation of the coherent Kondo lattice.Comment: to appear in Physical Review Letter

From caged compounds with isolated U atoms to frustrated magnets with 2- or 3-atom clusters: a review of Al-rich uranium aluminides with transition metals

International audienceCrystal structures and physical properties of four families of Al-rich ternary uranium compounds with transition metals () are reviewed, namely UAl, UAl, UAl, and UAl. The compounds can be described as consisting of 1 (isolated), 2 (dumbbells) or 3 (triangles) uranium atom clusters, surrounded (1-2-20, 1-2-10 and 6-4-43) or not (3-4-12) by large cages, which strongly influence their magnetic and related properties. Indeed, the ground states of the described systems evolve from Curie-like paramagnetism in the case of the phases with well-isolated, single U-atoms, to complex magnetic order or possible frustrated magnetism in the case of the systems with uranium triangles forming a breathing kagome lattice. We argue that the four families of uranium aluminides described in this review provide a unique opportunity to study magnetic interactions between U magnetic moments while gradually increasing the number of their nearest magnetic neighbors, and may also be helpful in understanding the fundamental origin of magnetic freezing phenomena

Magnetic, electric and thermoelectric properties of ternary intermetallics from the Ce-Co-Ge system

International audienceMagnetic susceptibility, magnetization, electrical resistivity and thermoelectric power of polycrystalline Ce2CoGe3, Ce3CoGe2, CeCo0.86Ge2, Ce5Co4Ge13, CeCoGe3, and Ce2Co3Ge5 were studied in wide temperature and magnetic field ranges. The results of magnetic properties and electrical resistivity measurements carried out for Ce3CoGe2, CeCo0.86Ge2, CeCoGe3 and Ce2Co3Ge5 corroborate the data reported in literature. Ce2CoGe3 and Ce5Co4Ge13 were found to be ferromagnetically ordered below 10 and 7 K, respectively. Moreover, the resistivity of Ce2CoGe3 shows Kondo-like behavior. The thermoelectric power exhibits in all six phases a large broad maximum, located between 50 and 150 K, most likely due to the presence of 4f electrons

Evolution of magnetic and transport properties in the Ce-Co-Ge ternary system

International audienceAmong the 10 phases reported to exist at 973 K in the Ce-Co-Ge ternary system, a strong dependence of the magnetic and transport properties on the constituent concentration has been evidenced. Close to the Ce-Ge binary axis, the ternary phases exhibit ferromagnetic-like ordering with low TC, while increasing the cobalt concentration leads first to a paramagnetic area, then to an antiferromagnetic one and finally to ferromagnetism with high TC for cobalt and Co-rich binaries. Similarly, electrical resistivity and thermopower measurements evidence a rather metallic behavior for cerium poor phases while an increase in the Ce-content results in an increase of the Kondo-like interactions

Competition of Magnetocrystalline Anisotropy of Uranium Layers and Zig-Zag Chains in UNi0.34_{0.34}Ge2_2 Single Crystals

Structural and thermodynamic properties of single-crystalline UNi$_{1-x}$Ge$_2$ with $x$\,=\,0.66 have been investigated by measuring magnetization, specific heat, and thermal expansion over a wide range of temperatures and magnetic fields. The measurements revealed the emergence of a long-range antiferromagnetic ordering of uranium magnetic moments below the N{\'e}el temperature $T_{\rm N}$\,=\,45.5\,K and the existence of two easy axes in the studied compound, namely $b$ and $c$, which correspond to the planes of the uranium zig-zag chains. Magnetic field applied along these two crystallographic directions induces in the system a first-order metamagnetic phase transition (from antiferromagnetism to field-polarized paramagnetism), and the width of the magnetic hysteresis associated with that transition reaches as much as 40 kOe at the lowest temperatures. A magnetic phase diagram developed from the experimental data showed that the metastable region associated with that magnetic hysteresis forms a funnel that narrows toward the N{\'e}el point in zero magnetic field. The four-layer Ising model has successfully predicted the collinear antiferromagnetic structure in UNi$_{0.34}$Ge$_2$ (known from earlier reports), its magnetic phase diagram, and temperature and field variations of its magnetization. Moreover, it suggests that the first-order phase transition extends down to zero magnetic field, although it is barely detectable in the experiments performed in low magnetic fields. According to this model, the second-order phase transition occurs in the compound only in zero field.Comment: 15 pages, 12 figure

Competition of magnetocrystalline anisotropy of uranium layers and zigzag chains in UNi0.34Ge2 single crystals

International audienceStructural and thermodynamic properties of single-crystalline UNi1-xGe2 with x = 0.66 have been investigated by measuring magnetization, specific heat, and thermal expansion over a wide range of temperatures and magnetic fields. The measurements revealed the emergence of a long-range antiferromagnetic ordering of uranium magnetic moments below the Neel temperature T-N = 45.5(1) K and the existence of two easy axes in the studied compound, namely, b and c, which correspond to the plane of the uranium zigzag chains. Magnetic field applied along these two crystallographic directions induces in the system a first-order metamagnetic phase transition (from antiferromagnetism to field-polarized paramagnetism), and the width of the magnetic hysteresis associated with that transition reaches as much as about 40 kOe at the lowest temperatures. A magnetic phase diagram developed from the experimental data showed that the metastable region associated with that magnetic hysteresis forms a funnel that narrows toward the Neel point in a zero magnetic field. The four-layer Ising model has successfully predicted the collinear antiferromagnetic structure in UNi0.34Ge2 (known from earlier reports), its magnetic phase diagram, and temperature and field variations of its magnetization. Moreover, it suggests that the first-order phase transition extends down to a zero magnetic field, although it is barely detectable in the experiments performed in low magnetic fields. According to this model, the second-order phase transition occurs in the compound only in a zero field