Magnetic and related properties of a novel compound Ce3Co2Sn7

International audienceA novel compound Ce7Co3Sn2 was synthesized and characterized by means of X-ray powder diffraction, magnetic susceptibility and magnetization, specific heat, electrical resistivity and magnetoresistivity measurements performed at temperatures down to 1.8 K and in magnetic fields up to 9 T. The compound was found to crystallize in the orthorhombic La3Co2Sn7 structure type (space group Cmmm, no. 65) with lattice parameters: a = 4.556(8) Å, b = 27.345(5) Å and c = 4.562(3) Å. Analysis of the physical properties suggests that only two of three atoms in the formula unit possess localized magnetic moments, which order antiferromagnetically at 4.6 K with some field-induced spin-reorientation in the ordered region. Moreover, Ce3Co2Sn7 exhibits some features of dense Kondo systems with the characteristic Kondo temperature of about 1.2 K

Antiferromagnetic ordering in the ternary uranium germanide UNi1–xGe2: Neutron diffraction and physical properties studies

International audienceThe compound UNi0.45Ge2 was studied by means of X-ray diffraction (XRD), magnetization, neutron diffraction, specific heat and electrical resistivity measurements performed in wide ranges of temperature and magnetic field. The single-crystal XRD experiment indicated that the material crystallizes in the orthorhombic CeNiSi2-type structure with the lattice parameters a = 4.1062(2) Å, b = 15.9272(8) Å and c = 4.0461(2) Å. The physical properties measurements showed that it orders antiferromagnetically at TN = 47 K. The magnetic ordering was confirmed by the neutron diffraction experiment, which revealed that the ordered magnetic moments are aligned along the crystallographic b-axis in a sequence −++−. In strong magnetic fields, a distinct field-induced first-order metamagnetic phase transition occurs, characterized by a large magnetic hysteresis. Temperature and field variations of the electrical resistivity are strongly affected by the atom disorder in the crystallographic unit cell of the investigated compound

The actinide-platinum binaries Th3Pt4 and U3Pt4: Crystallographic investigation and heavy-fermion behavior of the ferromagnetically ordered U3Pt4

International audienceThe existence of the binary compounds Th3Pt4 and U3Pt4 has been established in the course of the reinvestigation of the U-Pt and Th-Pt systems. Their structural and physical properties have been studied for the first time. Both compounds solidify from the melt of the elemental components with the stoichiometric ratio. Rietveld refinements reveal that they both adopt the trigonal Pu3Pd4 structure type (R3¯ space group) with lattice parameters at room temperature of a = 13.6870(3) Å, c = 5.7991(2) Å for Th3Pt4 and a = 13.2380(2) Å, c = 5.6808(2) Å for U3Pt4. Magnetic and specific heat measurements show that Th3Pt4 behaves as a typical metal; it was further used as phonon analogue of the U-counterpart. U3Pt4 undergoes a ferromagnetic ordering below TC = 6.5(5) K. Its low temperature specific heat is dominated by an enhanced Sommerfeld coefficient (246(2) mJ molU −1 K−2) classifying this phase into the heavy fermion family

Ferromagnetic ordering in UFe0.40Ge2 studied by 57Fe Mössbauer spectroscopy

International audienceA polycrystalline 57Fe-isotope-enriched sample of UFe0.40Ge2 was investigated by X-ray powder diffraction, magnetization and Mössbauer spectra measurements. The compound was confirmed to crystallize with the orthorhombic CeNiSi2-type structure (space group Cmcm) and with the lattice parameters a = 4.0759(2) Å, b = 15.8107(7) Å, and c = 4.0379(2) Å, being close to those reported previously for a very similar composition. Magnetic properties measurements showed that UFe0.40Ge2 orders ferromagnetically at TC = 37 K with the effective magnetic moment of 2.57(3) μB and the ordered magnetic moment at 70 kOe of about 0.64(1) μB, being fully consistent with the earlier report on physical properties of UFe0.39Ge2. 57Fe Mössbauer spectra measurements performed both in the field-cooled and zero-field-cooled regimes ruled out the formation of ferromagnetic cluster-glass or spin-glass state, and confirmed that the ferromagnetism in the studied system is purely long-range in nature. A small contribution of about 0.24–0.36 μB to the total magnetic moment from the iron atoms was observed

Magnetic and related properties of Ce5CoGe2, CeCoGe and CeCo2Ge2

International audienceMagnetic susceptibility, magnetization, specific heat, electrical resistivity and thermoelectric power of polycrystalline Ce5CoGe2, CeCoGe and CeCo2Ge2 were studied at temperatures down to 2 K and in magnetic fields up to 5 T. The novel phase Ce5CoGe2 was found to be a ferromagnet with the Curie temperature of about 11 K, which exhibits in the paramagnetic region some features of a dense Kondo system with strong crystal field effect. The re-investigated CeCoGe was found to order antiferromagnetically below 4.6 K, while CeCo2Ge2 is an intermediate-valence system, in agreement with previous reports. The thermoelectric power of the latter compound is large (up to 40 μV/K) and positive in the whole temperature range studied, while in the magnetically ordered systems Ce5CoGe2 and CeCoGe it is mostly negative and distinctly smaller (down to −1.5 and −11 μV/K, respectively)