[en] We report on the construction of a new high magnetic field user laboratory which will offer pulsed-field coils in the range (60 T, 500 ms, 40 mm) to (100 T, 10 ms, 20 mm) for maximum field, pulse time, and bore diameter of the coils. These coils will be energized by a modular 50 MJ/24 kV capacitor bank. Besides many other experimental techniques, as unique possibilities NMR in pulsed fields as well as infrared spectroscopy at 5 to 150 μm will be available by connecting the pulsed field laboratory to a nearby free-electron-laser facility

[en] Heavy fermion compounds are host to many interesting but poorly understood strong correlation effects, leading in exceptional cases to unconventional superconductivity. CeCoIn₅ is such an example of an ambient pressure heavy fermion superconductor with a T_c of 2.3K. Such compounds are best described as a Kondo lattice, where Ce, Yb or U ions form a periodic lattice of magnetic moments coupled to the conduction electrons via antiferromagnetic exchange interaction. Dilution, or substitution, of the Kondo ion with a lanthanide, actinide or alkali-earth element that does not participate in the Kondo lattice, results in the so-called ^Kondo hole^. The electron scattering off the Kondo hole leads to significant changes in both the normal and superconducting properties. We have investigated the suppression of superconductivity in CeCoIn₅ diluted with La, Yb, Y, Ca, Th, Gd, Er, Eu and Lu via specific heat measurements on well characterized single crystals. The suppression of the superconducting condensation energy exhibits a remarkable departure from the Abrikosov-Gorkov impurity pair breaking picture, emphasizing that the Kondo holes are no ordinary pair-breakers.

[en] We present measurements of the low temperature Hall effect and magnetoresistance in the heavy fermion superconductor CeCo(In_0.925Cd_0.075)₅ as a function of applied magnetic field. The Hall resistivity ρ_xy is observed to be negative indicating electron dominated transport. Features corresponding to the possible destabilization of the antiferromagnetic ground state are observed. Magnetic field sweeps show that the resistivity ρ_xx(H) is hysteretic in this regime, indicating that these transitions could be first order in nature.

[en] The Life Extension Program for the PHWR Embalse power reactor of Argentina includes the replacement of de original set of 2,5% Nb pressure tubes by a new one It was also decided to made the new set de pressure tubes locally from imported Zr-2,5% Nb extruded tubes. Based on the degraded processes that develop in service a new set of metallurgical requirements was set by the Designer to be follow for new suppliers. As the mechanical properties of pressure tubes in operation depend on the micro-structural deformation, it is necessary to add to the normal macroscopic quality control same additional mechanical and microstructural studies, especially during the development stage. In the present paper the current status of delay hydrogen cracking, full width at half maximum (FWHM) of x-ray diffraction peaks, alpha phase thickness log-normal distributions and Kearns texture factors are summarized to estimate the magnitude of the micro-structural characteristics of pressure tubes obtained from imported Zr-2,5% Nb extruded tubes that were processes following designer specifications. The pressure tubes were obtained by two step of plastic deformation in a HPTR 60-120 tube rolling machine without intermediate annealing and a final thermal treatment (author)

[en] Differential conductance spectra are taken from metallic point-contact junctions on Cd-doped CeCoIn₅. For (100) junctions with nominal 10% doping, we observe signatures for subsequent antiferromagnetic and superconducting transitions in qualitative agreement with bulk measurements. In the superconducting state, two conductance channels compete, both with enhanced subgap conductance, one due to superconductivity and the other antiferromagnetism. The conductance data exhibit variances for different doping levels and crystallographic orientations and junction to junction. This issue will be addressed further in terms of surface inhomogeneity or intrinsic nonuniform phase formation.

[en] We report on the recent progress made at the Dresden High Magnetic Field Laboratory (Hochfeld-Magnetlabor Dresden = HLD). This facility, under construction at the research center (Forschungszentrum) Rossendorf, is planned to open as user facility in 2007 offering access to various pulsed-field magnets. Besides the ultimate goal of constructing a multi-pulse magnet reaching 100T in a bore of 20mm with a peak-pulse duration of about 10 ms, further self-designed high-energy coils will be provided. For thermodynamic experiments, e.g., a pulsed coil for 60T in 40mm and 1 s is planned. The necessary energy of up to 50MJ for coil operation recently became available through a world-unique capacitor bank working at 24 kV. First user-type magnets for fields up to 71T for 100ms in a bore of 24mm have been tested successfully. As an outstanding feature of the laboratory, the bright light of a next-door free-electron-laser facility will allow dedicated high-field infrared spectroscopy. A broad range of experimental techniques is being developed both for user and in-house research in static and pulsed magnetic fields

[en] Angular-dependent de Haas-van Alphen measurements allow the mapping of Fermi surfaces in great detail with high accuracy. Density functional electronic-structure calculations can be carried out with high precision, but depend crucially on the used structural information and the applied calculational approximations. We report in a detailed study the sensitivity of the calculated electronic band structure of the 122 compound LaFe₂P₂ on (i) the exact P position in the unit cell, parametrized by a so-called z parameter, and on (ii) the treatment of the La 4f  states. Depending on the chosen exchange and correlation-potential approximation, the calculated z parameter varies slightly and corresponding small but distinctive differences in the calculated band structure and Fermi-surface topology appear. Similarly, topology changes appear when the energy of the mostly unoccupied La 4f  states is corrected regarding their experimentally observed position. The calculated results are compared to experimental de Haas-van Alphen data. Our findings show a high sensitivity of the calculated band structure on the pnictide z position and the need for an accurate experimental determination of this parameter at low temperatures, and a particular need for a sophisticated treatment of the La 4f  states. Thus, this is not only crucial for the special case of LaFe₂P₂ studied here, but of importance for the precise determination of the band structure of related 122 materials and La containing compounds in general. (paper)

[en] The intermetallic compound Pr_1-x-yLa_xPb_yTe shows a wide spectrum of physical phenomena. Depending on the metallurgical composition as function of x and y, the compound changes its behavior from van Vleck paramagnetism and hyperfine-enhanced nuclear-magnetic order to super- or semiconductivity. In addition, there are remarkable interplay effects between these ground states. In consequence, Pr_1-x-yLa_xPb_yTe may serve as an interesting material for nuclear-spin quantum-computing experiments. In this contribution, we focus on measurements of the magnetic properties performed in high magnetic fields. We present first data of the magnetization of Pr_1-yPb_yTe taken in pulsed magnetic fields up to 47 T for the compositions y = 0, 50, and 90 %

[en] The thermal conductivities of stoichiometric CaB₆, vacancy-doped Ca_1-δB₆, and EuB₆ have been measured between 6 and 300 K. All our data may be rather well described across the entire temperature regime covered on the basis of a Debye-type relaxation-time approximation and by assuming the concurring influence of various scattering channels on the mean free path of the phonons. An unusual and strong resonance in the scattering rate of the phonons of all investigated materials is attributed to a strong interaction between acoustic itinerant and localized modes, the latter arising from oscillations of the metal cations around their equilibrium position

[en] Muon spin relaxation ( μ SR) measurements were carried out on SrDy₂O₄, a frustrated magnet featuring short range magnetic correlations at low temperatures. Zero-field muon spin depolarization measurements demonstrate that fast magnetic fluctuations are present from T = 300 K down to 20 mK. The coexistence of short range magnetic correlations and fluctuations at T = 20 mK indicates that SrDy₂O₄ features a spin liquid ground state. Large longitudinal fields affect weakly the muon spin depolarization, also suggesting the presence of fast fluctuations. For a longitudinal field of μ₀ H = 2 T, a non-relaxing asymmetry contribution appears below T = 6 K, indicating considerable slowing down of the magnetic fluctuations as field-induced magnetically-ordered phases are approached. (paper)