227 research outputs found
X-Ray Diffuse Scattering in N-Methylphenazinium-Tetracyanoquinodimethane (NMP-TCNQ)(Physics)
X-ray diffuse scattering measurements of NMP-TCNQ at room temperature reveal some parts of diffuse lines at heights (l±0 : 094n) a^* from the b^*-c^* plane (l and n are integers, and n varies from 0 to 5). These diffuse lines, except those of the 0th order, can be interpreted in terms of a phonon anomaly and suggest incomplete cation-anion charge transfer in NMP-TCNQ
Single Crystal Growth of Skutterudite CoP3 under High Pressure
A new method to grow single crystals of skutterudite compounds is examined.
Using a wedge-type, cubic-anvil, high-pressure apparatus, single crystals of
CoP3 were grown from stoichiometric melts under a pressure of 3.5 GPa. Powder
x-ray diffraction and electron probe microanalysis measurements indicate that
the as-grown boules are a single phase of CoP3. The results suggest that CoP3
is a congruent melting compound under high pressure.Comment: 6pages,5 figures, J. Crystal Growth (in press
31P-NMR and muSR Studies of Filled Skutterudite Compound SmFe4P12: Evidence for Heavy Fermion Behavior with Ferromagnetic Ground State
The 31P-NMR (nuclear magnetic resonance) and muSR (muon spin relaxation)
measurements on the filled skutterudite system SmFe4P12 have been carried out.
The temperature T dependence of the 31P-NMR spectra indicates the existence of
the crystalline electric field effect splitting of the Sm3+$ (J = 5/2)
multiplet into a ground state and an excited state of about 70 K. The
spin-lattice relaxation rate 1/T1 shows the typical behavior of the Kondo
system, i.e., 1/T1 is nearly T independent above 30 K, and varies in proportion
to T (the Korringa behavior, 1/T1 \propto T) between 7.5 K and 30 K. The T
dependence deviated from the Korringa behavior below 7 K, which is independent
of T in the applied magnetic field of 1 kOe, and suppressed strongly in higher
fields. The behavior is explained as 1/T1is determined by ferromagnetic
fluctuations of the uncovered Sm3+ magnetic moments by conduction electrons.
The muSR measurements in zero field show the appearance of a static internal
field associated with the ferromagnetic order below 1.6 K.Comment: 6 pages, 9 figures, to be published in J. Phys. Soc. Jpn. 75 (2006
Charge-Density-Wave Ordering in the Metal-Insulator Transition Compound PrRu4P12
X-ray and electron diffraction measurements on the metal-insulator (M-I)
transition compound PrRuP have revealed the emergence of a periodic
ordering of charge density around the Pr atoms. It is found that the ordering
is associated with the onset of a low temperature insulator phase. These
conclusions are supported by the facts that the space group of the crystal
structure transforms from Im to Pm below the M-I transition
temperature and also that the temperature dependence of the superlattice peaks
in the insulator phase follows the squared BCS function. The M-I transition
could be originated from the perfect nesting of the Fermi surface and/or the
instability of the electrons.Comment: 4 pages, 5 figures, Phys. Rev. B (2004) (in press
Metal-insulator transition in PrRuP and SmRuP investigated by optical spectroscopy
Electronic structures of the filled-skutterudite compounds PrRuP
and SmRuP, which undergo a metal-insulator transition (MIT) at
= 60 K and 16 K, respectively, have been studied by means of
optical spectroscopy. Their optical conductivity spectra develop an energy gap
of 10 meV below . The observed characteristics of the energy
gap are qualitatively different from those of the Kondo semiconductors. In
addition, optical phonon peaks in the spectra show anomalies upon the MIT,
including broadening and shifts at and an appearance of new peaks
below . These results are discussed in terms of density waves or
orbital ordering previously predicted for these compounds.Comment: 4pages, 4figures, submitted to Physical Review
Superconductivity and the high field ordered phase in the heavy fermion compound PrOsSb
Superconductivity is observed in the filled skutterudite compound \PrOsSb{}
below a critical temperature temperature K and appears to
develop out of a nonmagnetic heavy Fermi liquid with an effective mass , where is the free electron mass.
Features associated with a cubic crystalline electric field are present in
magnetic susceptibility, specific heat, electrical resistivity, and inelastic
neutron scattering measurements, yielding a Pr energy level scheme
consisting of a nonmagnetic doublet ground state, a low lying
triplet excitied state at K, and much higher temperature
triplet and singlet excited states. Measurements also
indicate that the superconducting state is unconventional and consists of two
distinct superconducting phases. At high fields and low temperatures, an
ordered phase of magnetic or quadrupolar origin is observed, suggesting that
the superconductivity may occur in the vicinity of a magnetic or quadrupolar
quantum critical point.Comment: 11 pages, 4 figures, presented at the 3rd international symposium on
Advance Science Research (ASR 2002), JAERI Tokai, Ibaraki, Japa
Anomalous elastic softening of SmRu_{4}P_{12} under high pressure
The filled skutterudite compound SmRu_4P_{12} undergoes a complex evolution
from a paramagnetic metal (phase I) to a probable multipolar ordering insulator
(phase II) at T_{MI} = 16.5 K, then to a magnetically ordered phase (phase III)
at T_{N} = 14 K. Elastic properties under hydrostatic pressures were
investigated to study the nature of the ordering phases. We found that distinct
elastic softening above T_{MI} is induced by pressure, giving evidence of
quadrupole degeneracy of the ground state in the crystalline electric field. It
also suggests that quadrupole moment may be one of the order parameters below
T_{MI} under pressure. Strangely, the largest degree of softening is found in
the transverse elastic constant C_{T} at around 0.5-0.6 GPa, presumably having
relevancy to the competing and very different Gruneisen parameters \Omega of
T_{MI} and T_{N}. Interplay between the two phase transitions is also verified
by the rapid increase of T_{MI} under pressure with a considerably large \Omega
of 9. Our results can be understood on the basis of the proposed octupole
scenario for SmRu_4P_{12}.Comment: 7 pages, 7 figure
Assembling the puzzle of superconducting elements: A Review
Superconductivity in the simple elements is of both technological relevance
and fundamental scientific interest in the investigation of superconductivity
phenomena. Recent advances in the instrumentation of physics under pressure
have enabled the observation of superconductivity in many elements not
previously known to superconduct, and at steadily increasing temperatures. This
article offers a review of the state of the art in the superconductivity of
elements, highlighting underlying correlations and general trends.Comment: Review, 10 pages, 11 figures, 97 references; to appear in Superc.
Sci. Techno
Evidence for Magnetic Ordering Associated with Metal-Insulator Transition in SmRu4P12 Studied by Muon Spin Relaxation
Muon spin relaxation measurements on the filled skutterudite compound
SmRu4P12 have been carried out in zero- and longitudinal-fields. Temperature
dependence of both initial asymmetry and muon-spin depolarization rate show the
appearance of a magnetically ordered state below the metal-insulator transition
temperature TMI. The present study indicates that the ordering below TMI is not
a non-magnetic antiferro-quadrupolar ordering but a magnetic one, which
supports a scenario that a magnetic octupolar ordering occurs below TMI in
SmRu4P12.Comment: 5 pages, 5 figures, Phys. Rev. B 73, 052408 (2006
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