Magnetic behavior in UFe?Zn?? and URu?Zn?? single crystals

The magnetic, electrical transport and thermodynamic properties of the compounds UFe?Zn?? and URu?Zn?? were studied on single-crystalline specimens over wide ranges of temperature and magnetic field. The results indicate that the two ternaries are paramagnetic moderately enhanced heavy fermion systems. Their physical behavior is governed predominantly by the hybridization of uranium 5f orbitals with electronic states of ligands, which brings about considerable delocalization of the 5f states.     

Amorphous Ge??Te??: density functional, high-energy x-ray and neutron diffraction study

The structure and electronic properties of amorphous Ge(15)Te(85) have been studied by combining density functional (DF) simulations with high-energy x-ray and neutron diffraction measurements. Three models with 560 atoms have been constructed using reverse Monte Carlo methods constrained to (1) agree with the experimental structure factors S(Q), and have (2) energies close to the DF minimum and (3) a semiconducting band structure. The best structure is based on the melt-quenched DF structure and has a small number of Ge-Ge bonds. It shows interlocking networks of Te and GeTe with a significant fraction (22-24%) of voids (cavities). Ge occurs with both tetrahedral and 3 + 3 defective octahedral configurations, and the coordination of Te is slightly higher than indicated by the '8 - N rule' (N is the number of valence electrons). The GeTe network includes clusters of ABAB squares (A = Ge, B = Te), and the bonding is characterized by the chemical bond orders.     

Vibrations of Au?? and FeAu?? nanoparticles and the limits of the Debye temperature concept

We present first-principles calculations of the vibrational density of states (VDOS), the specific heat and the mean-squared displacement of the five lowest-energy isomers of Au(13) and of two low-energy FeAu(12) nanoparticles. We find that the vibrational contributions to the Helmholtz energy do not affect the energy ordering of the isomers. As expected, for nanoparticles the vibrational density of states differs dramatically from the function proposed by the Debye model. We demonstrate that, for the nanoclusters we studied, the alternative calculations of the 'Debye temperature' yield significantly inconsistent results. We conclude that T(D) obtained from a particular thermodynamic property is neither applicable for deriving conclusions about other thermodynamic properties nor correlated with atomic bond strengths. Instead, in order to describe the temperature dependence of a nanoparticle's mean-squared displacement and its specific-heat capacity, what is necessary is its discrete phonon spectrum.     

First-principles phonon calculations of Fe?? impurity in SrTiO?

The results of hybrid density functional theory calculations on phonons in Sr(Fe(x)Ti(1-x))O(3) solid solution within the formalism of a linear combination of atomic orbitals are presented. The phonon density of states (DOS) calculated for 6.25% Fe(4+) impurities is reported and defect-induced phonon modes are identified. Based on our calculations and group-theoretical analysis, we suggest for the first time an interpretation of experimentally observed Raman- and IR-active modes.     

Physical properties and valence state of cerium in the filled skutterudite CePt?Ge??

Electronic, magnetic, and transport properties of the filled platinum-germanium skutterudite CePt?Ge?? are investigated. High resolution x-ray absorption spectroscopy measurements at the cerium L(III) edge demonstrate that CePt?Ge?? in this compound has a temperature-independent valence close to three. However, magnetic susceptibility, thermopower, Hall effect, and electronic specific heat reveal a broad maximum at Tmax D 65-80 K, suggesting the presence of valence fluctuations. The Sommerfeld coefficient γ = 105 mJ mol?1 K?2, deduced from specific heat, indicates moderately enhanced band masses for CePt?Ge??. We discuss these findings and conclude that CePt?Ge?? represents a system at the border between intermediate valence (IV) and Kondo lattice behavior. In addition, the lattice specific heat and the thermal conductivity are discussed with respect to the vibrational dynamics of Ce in the [Pt?Ge??] framework.     

Response of Granular La1??xCaxMnO3 Film to 10?GHz and 35?GHz Frequency Electromagnetic Radiation

The nonbolometric response of La_1 − xCa_xMnO₃ film to 10 GHz and 35 GHz frequency electromagnetic radiation is investigated in the case when, in addition to the strong electric field of the wave, the film is subjected to a stationary electric bias field. Dependences of responses on the radiation power P at temperature T = 80 K are presented. In the low power region, a linear dependence of the response on P is observed at both frequencies whereas for high powers the dependence behaves as ~P ^1/2. The obtained results are explained taking into account that the nonbolometric response originates from the intergranular junctions that operate in the reverse current regime. There two effects take place: (i) at low powers the detection resistance decreases with increasing power P, and (ii) at higher powers in addition to that the film resistance decreases as P ^1/2 due to the avalanche of charge carriers in the electric field of the electromagnetic wave.     

Search for a SM Higgs boson in dilepton plus missing transverse energy final state with the D??detector at {\sqrt s}{=}{1.96}?TeV

A search is presented for the Standard Model (SM) Higgs boson optimized in the decay channel H??W ^?+? W ^??, where both W bosons decay leptonically. The final state considered contains dileptons and missing transverse energy from the neutrinos. A multivariate analysis is used to suppress the background. No significant excess above the SM background has been observed and limits set on the Higgs boson production cross-section ? the branching ratio for m _H?= 115?C200?GeV are computed. Results using 8.1?fb^?1 of data are presented.