1,586 research outputs found
Anomalous Raman scattering from phonons and electrons of superconducting FeSe
We report interesting anomalies in the temperature dependent Raman spectra of
FeSe measured from 3K to 300K in the spectral range from 60 to 1800
cm and determine their origin using complementary first-principles
density functional calculations. A phonon mode near 100 cm exhibits a
sharp increase by 5% in frequency below a temperature T ( 100
K) attributed to strong spin-phonon coupling and onset of short-range
antiferromagnetic order. In addition, two high frequency modes are observed at
1350 cm and 1600 cm, attributed to electronic Raman scattering
from ()to / -orbitals of Fe.Comment: 19 pages, 4 figures, 1 tabl
Thermal and spectrodcopic studies on the decomposition of [Ni{di(2-aminoethyl)amine}2] and [Ni(2,2':6',2"-terpyridine)2] Montmorillonite intercalated composites
Intercalated [Ni{di(2-aminoethyl)amine}2]-Montmorillonite (I) and [Ni(2,20:60,200-terpyridine)2]-Montmorillonite (II)
composites have been synthesized and their thermal behavior studied by TG, DTG and DTA substantiated by XRD and IR
spectroscopy. Thermal stabilities of the composites I and II were about 50 and 1508C higher, respectively, compared to their
respective free metal complex salts. These results indicate that the metal complex with aromatic backboned ligands had higher
thermal stability than that of the aliphatic one upon intercalation into layered clay. XRD data showed that on heating, the basal
spacing (d001) of the I composite decreased gradually from 14.5
A ferromagnet with a glass transition
We introduce a finite-connectivity ferromagnetic model with a three-spin
interaction which has a crystalline (ferromagnetic) phase as well as a glass
phase. The model is not frustrated, it has a ferromagnetic equilibrium phase at
low temperature which is not reached dynamically in a quench from the
high-temperature phase. Instead it shows a glass transition which can be
studied in detail by a one step replica-symmetry broken calculation. This spin
model exhibits the main properties of the structural glass transition at a
solvable mean-field level.Comment: 7 pages, 2 figures, uses epl.cls (included
Temperature-dependent Raman study of CeFeAsO0.9F0.1 Superconductor: Crystal field excitations, phonons and their coupling
We report temperature-dependent Raman spectra of CeFeAsO0.9F0.1 from 4 K to
300 K in spectral range of 60 to 1800 cm-1 and interpret them using estimates
of phonon frequencies obtained from first-principles density functional
calculations. We find evidence for a strong coupling between the phonons and
crystal field excitations; in particular Ce3+ crystal field excitation at 432
cm-1 couples strongly with Eg oxygen vibration at 389 cm-1 . Below the
superconducting transition temperature, the phonon mode near 280 cm-1 shows
softening, signaling its coupling with the superconducting gap. The ratio of
the superconducting gap to Tc thus estimated to be ~ 10 suggests CeFeAsO0.9F0.1
as a strong coupling superconductor. In addition, two high frequency modes
observed at 1342 cm-1 and 1600 cm-
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