13 research outputs found
Evidence of momentum dependent hybridization in Ce2Co0.8Si3.2
We studied the electronic structure of the Kondo lattice system Ce2Co0.8Si3.2
by angle-resolved photoemission spectroscopy (ARPES). The spectra obtained
below the coherence temperature consist of a Kondo resonance, its spin-orbit
partner and a number of dispersing bands. The quasiparticle weight related to
the Kondo peak depends strongly on Fermi vectors associated with bulk bands.
This indicates a highly anisotropic hybridization between conduction band and
4f electrons - V_{cf} in Ce2Co0.8Si3.2.Comment: 6 page
Single-Crystal Growth of f-Electron Intermetallics in a Tetra-Arc Czochralski Furnace
The Czochralski technique has induced technological revolution in the electronic industry. It has also been widely used in the fundamental research area, as it allows obtaining high-quality single crystals of large variety of binary, ternary and multinary compounds. The unique tetra-arc Czochralski furnace installed at the Institute of Low Temperature and Structure Research, Polish Academy of Sciences in Wrocław, described in detail in the article, has been used to prepare a large number of single crystals of various Ce- and U-based intermetallic phases. Their excellent quality has facilitated advanced investigations of their anisotropic, often highly unusual physical properties
Ferromagnetic and spin-glass properties of single-crystalline U 2 NiSi 3
A single crystal of U 2 NiSi 3 was investigated by means of magnetization, electrical resistivity and heat capacity measurements. Whereas the DC magnetic data clearly manifest strongly anisotropic ferromagnetism, the AC magnetic susceptibility data are consistent with spin-glass behaviour, reported previously for polycrystalline samples. Moreover, no distinct anomalies around T C occur in the specific heat and electrical resistivity characteristics. Altogether the results obtained for single-crystalline U 2 NiSi 3 indicate rather an unusual state of coexistence of ferromagnetism and spin-glass freezing
Quantum Interference in Disordered Ferromagnet U₂NiSi₃
A single-crystalline sample of disordered ferromagnetic U₂NiSi₃ was investigated by means of electrical resistivity measurements under ambient and high hydrostatic pressure. Temperature dependences of the electrical resistivity clearly reveal interplay of the ferromagnetic ordering and quantum interference effects resulting from crystallographic disorder. Electron-electron interaction manifests itself as a increase in the in-plane and out-of-plane electrical resistivity below 5 K. Weak localization is observed solely in the ab-plane as a linear-in-T contribution to resistivity, which suggests that internal magnetic field does not break the interference of scattered electron waves in ab-plane. Applied hydrostatic pressure does not affect the electron-electron interaction contribution, however it diminishes the impact of weak localization on the ab-plane resistivity
Thermoelectric Power of Single-Crystalline
High-quality single crystal of was studied by means of thermoelectric power measurements carried out down to 2 K in external magnetic fields up to 13 T. The results obtained above 50 K were interpreted in terms of a modified two-band model that takes into account temperature variation of the width of 4f-derived narrow band located near the Fermi level. At lower temperatures the thermopower exhibits more complex temperature dependences that likely involve interplays of magnetic exchange, Kondo and crystal-field interactions
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
Antiferromagnetic Ordering and Transport Anomalies in Single-Crystalline CeAgAs<sub>2</sub>
Single crystals of the ternary cerium arsenide CeAgAs(2)were grown by chemical vapor transport. They were studied by means of x-ray diffraction, magnetization, heat capacity and electrical transport measurements. The experimental research was supplemented with electronic band structure calculations. The compound was confirmed to order antiferromagnetically at the Neel temperature of 4.9 K and to undergo metamagnetic transition in a field of 0.5 T at 1.72 K. The electrical resistivity shows distinct increase at low temperatures, which origin is discussed in terms of pseudo-gap formation in the density of states at the Fermi level and quantum corrections to the resistivity in the presence of atom disorder due to crystal structure imperfections
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