Structural phase transitions and their influence on Cu+ mobility in superionic ferroelastic Cu6PS5I single crystals

The structural origin of Cu+ ions conductivity in Cu6PS5I single crystals is described in terms of structural phase transitions studied by X-ray diffraction, polarizing microscope and calorimetric measurements. Below the phase transition at Tc=(144-169) K Cu6PS5I belongs to monoclinic, ferroelastic phase, space group Cc. Above Tc crystal changes the symmetry to cubic superstructure, space group F-43c (a=19.528); finally at 274K disordering of the Cu+ ions increases the symmetry to F-43m, (a=9.794). The phase transition at 274K coincides well with a strong anomaly in electrical conductivity observed in the Arrhenius plot. Diffusion paths for Cu+ ions are evidenced by means of the atomic displacement factors and split model. Influence of the copper stechiometry on the Tc is also discussed.Comment: conference pape

Dy8SnS13.61O0.39 from single-crystal data

Crystals of the title dysprosium tin sulfide oxide, Dy8SnS13S1−xOx [x = 0.39 (4)], were obtained unintentionally from the Dy–Sn–S system. A statistical mixture of sulfur and oxygen was assumed for one position in the structure. S and O atoms surround each of the eight symmetrically non-equivalent dysprosium atoms. The Sn atoms are located in tetra­hedral surroundings of sulfur atoms. Trigonal prisms and tetra­hedra are connected to each other by their edges. All atoms are situated in mirror planes

Performances of multi-gap timing RPCs for relativistic ions in the range Z=1-6

We present the performance of Multi-gap timing RPCs under irradiation by fully stripped relativistic ions (gamma*beta=2.7, Z=1-6). A time resolution of 80 ps at high efficiency has been obtained by just using standard `off the shelf' 4-gap timing RPCs from the new HADES ToF wall. The resolution worsened to 100 ps for ~ 1 kHz/cm2 proton flux and for ~ 100 Hz/cm2 Carbon flux. The chambers were operated at a standard field of E=100 kV/cm and showed a high stability during the experiment, supporting the fact that RPCs are a convenient choice when accommodating a very broad range of ionizing particles is needed. The data provides insight in the region of very highly ionizing particles (up to x 36 mips) and can be used to constrain the existing avalanche and Space-Charge models far from the usual `mip valley'. The implications of these results for the general case of detection based on secondary processes (n, gamma) resulting in highly ionizing particles with characteristic energy distributions will be discussed, together with the nature of the time-charge correlation curve.Comment: 31 pages, 19 figures, submitted to JINS

Inelastic neutron scattering studies of Crystal Field Levels in PrOs4_4As12_{12}

We use neutron scattering to study the Pr$^{3+}$ crystalline electric field (CEF) excitations in the filled skutterudite PrOs$_4$As$_{12}$. By comparing the observed levels and their strengths under neutron excitation with the theoretical spectrum and neutron excitation intensities, we identify the Pr$^{3+}$ CEF levels, and show that the ground state is a magnetic $\Gamma_4^{(2)}$ triplet, and the excited states $\Gamma_1$, $\Gamma_4^{(1)}$ and $\Gamma_{23}$ are at 0.4, 13 and 23 meV, respectively. A comparison of the observed CEF levels in PrOs$_4$As$_{12}$ with the heavy fermion superconductor PrOs$_4$Sb$_{12}$ reveals the microscopic origin of the differences in the ground states of these two filled skutterudites.Comment: 7 pages, 7 figure

Non-Fermi liquid behavior in a fluctuating valence system, the filled skutterudite compound CeRu_{4}As_{12}

Electrical resistivity $\rho$, specific heat C, and magnetic susceptibility $\chi$ measurements made on the filled skutterudite CeRu_4As_{12} reveal non-Fermi liquid (NFL) T - dependences at low T, i.e., $\rho$(T) $\sim$ T^{1.4} and weak power law or logarithmic divergences in C(T)/T and $\chi$(T). Measurements also show that the T - dependence of the thermoelectric power S(T) deviates from that seen in other Ce systems. The NFL behavior appears to be associated with fluctuations of the Ce valence between 3^+ and 4^+ rather than a typical Kondo lattice scenario that would be appropriate for an integral Ce valence of 3^+.Comment: 18 pages, 5 figure

A de Haas-van Alphen study of the filled skutterudite compounds PrOs4_4As12_{12} and LaOs4_4As12_{12}

Comprehensive magnetic-field-orientation dependent studies of the susceptibility and de Haas-van Alphen effect have been carried out on single crystals of the filled skutterudites PrOs$_4$As$_{12}$ and LaOs$_4$As$_{12}$ using magnetic fields of up to 40~T. Several peaks are observed in the low-field susceptibility of PrOs$_4$As$_{12}$, corresponding to cascades of metamagnetic transitions separating the low-field antiferromagnetic and high-field paramagnetic metal (PMM) phases. The de Haas-van Alphen experiments show that the Fermi-surface topologies of PrOs$_4$As$_{12}$ in its PMM phase and LaOs$_4$As$_{12}$ are very similar. In addition, they are in reasonable agreement with the predictions of bandstructure calculations for LaOs$_4$As$_{12}$ on the PrOs$_4$As$_{12}$ lattice. Both observations suggest that the Pr 4$f$ electrons contribute little to the number of itinerant quasiparticles in the PMM phase. However, whilst the properties of LaOs$_4$As$_{12}$ suggest a conventional nonmagnetic Fermi liquid, the effects of direct exchange and electron correlations are detected in the PMM phase of PrOs$_4$As$_{12}$. For example, the quasiparticle effective masses in PrOs$_4$As$_{12}$ are found to decrease with increasing field, probably reflecting the gradual suppression of magnetic fluctuations associated with proximity to the low-temperature, low-field antiferromagnetic state

A large area timing RPC prototype for ion collisions in the HADES spectrometer

We present a resistive plate chamber (RPC) prototype for time-of-flight measurements over large areas and at high occupancies, minimizing the inter-channel cross-talk.http://www.sciencedirect.com/science/article/B6TJM-4D75GPD-9/1/a6fe40c114a867a0f98e2fec0f13350

Deep sub-threshold Ξ−\Xi^- production in Ar+KCl reactions at 1.76A GeV

We report first results on a deep sub-threshold production of the doubly strange hyperon $\Xi^-$ in a heavy-ion reaction. At a beam energy of 1.76A GeV the reaction Ar+KCl was studied with the High Acceptance Di-Electron Spectrometer (HADES) at SIS18/GSI. A high-statistics and high-purity $\Lambda$ sample was collected, allowing for the investigation of the decay channel $\Xi^- \to \Lambda \pi^-$. The deduced $\Xi^-/(\Lambda+\Sigma^0)$ production ratio of $(5.6 \pm 1.2 ^{+1.8}_{-1.7})\cdot 10^{-3}$ is significantly larger than available model predictions.Comment: 4 pages, including 4 figure

Inclusive Dielectron Production in Ar+KCl Collisions at 1.76 AGeV studied with HADES

Results of the HADES measurement of inclusive dielectron production in Ar+KCl collisions at a kinetic beam energy of 1.76 AGeV are presented. For the first time, high mass resolution spectroscopy was performed. The invariant mass spectrum of dielectrons is compared with predictions of UrQMD and HSD transport codes.Comment: 4 pages, 3 figures - To appear in the conference proceedings for Quark Matter 2009, March 30 - April 4, Knoxville, Tennesse

Dilepton production in pp and CC collisions with HADES

Dilepton production has been measured with HADES, the "High Acceptance DiElectron Spectrometer". In pp collisions at 2.2GeV kinetic beam energy, exclusive eta production and the Dalitz decay eta -> gamma e+e- has been reconstructed. The electromagnetic form factor is well in agreement with existing data. In addition, an inclusive e+e- spectrum from the C+C reaction at 2AGeV is presented and compared with a thermal model.Comment: 11 pages, 3 figures, proceedings of the IVth International Conference on Quarks and Nuclear Physics, Madrid, June 5th-10th, submitted to Eur.Phys.J.