44 research outputs found
The Transition from Heavy Fermion to Mixed Valence in Ce1-xYxAl3: A Quantitative Comparison with the Anderson Impurity Model
We present a neutron scattering investigation of Ce1-xYxAl3 as a function of
chemical pressure, which induces a transition from heavy-fermion behavior in
CeAl3 (TK=5 K) to a mixed-valence state at x=0.5 (TK=150 K). The crossover can
be modeled accurately on an absolute intensity scale by an increase in the k-f
hybridization, Vkf, within the Anderson impurity model. Surprisingly, the
principal effect of the increasing Vkf is not to broaden the low-energy
components of the dynamic magnetic susceptibility but to transfer spectral
weight to high energy.Comment: 4 pages, 5 figure
Phonon density-of-states in the new superconductor MgB
We provide here experimental data on the phonon density-of-states of MgB2
obtained by the inelastic neutron scattering technique. The measurements were performed
for the natural boron-based magnesium diboride with use of a time-of-flight neutron
spectrometer. Several phonon bands were observed in the phonon spectrum at energies of
about 33, 55, 82 and 99 meV. We show that the cut-off energy of the density-of-states
occurs at around 105 meV which is much higher than expected so far from heat-capacity
data and partially explains the high Tc value observed for MgB2. The characteristic phonon
energies are indicative of an intermediate coupling regime in this compound. We conclude
that a much needed neutron experiment aimed at the study of the isotopic effect in the
phonon density-of-states of MgB2 is conceivable
Polarized infrared and neutron scattering studies of alpha-Bi<sub>2</sub>O<sub>3</sub>
Studies on the lattice dynamics of ct-Bi203 have been performed including IR polarized reflectance spectra on single crystal, inelastic neutron scattering and specific heat measurements. Dispersion parameters and polarizations of IRactive phonons are presented and compared with neutron and specific heat data