1,166 research outputs found
Evolution of crystalline electric field effects, superconductivity, and heavy fermion behavior in the specific heat of Pr(OsRu)Sb
Specific heat measurements were made on single crystals of the
superconducting filled skutterudite series Pr(OsRu)Sb
down to 0.6 K. Crystalline electric field fits in the normal state produced
parameters which were in agreement with previous measurements. Bulk
superconductivity was observed for all values of the Ru concentration with
transition temperatures consistent with previous experiments, confirming a
minimum in at . The data below appear to be more
consistent with power law behavior for (PrOsSb), and with
exponential behavior for . An enhanced electronic
specific heat coefficient was observed for , further
supporting as a critical concentration where the physical
properties abruptly change. Significant enhancement of above
the weak coupling value was only observed for and .Comment: 16 pages, 5 figures, submitted to Physical Review B. v2: text added
and figures modifie
Impurity induced density of states and residual transport in nonunitary superconductors
We obtain general expressions for the residual density of states, electrical
conductivity and thermal conductivity for non-unitary superconductors due to
impurity scattering. We apply the results to the so-called `B phase' of
PrOs4Sb12, which we describe using a non-unitary gap function derived from
symmetry considerations. The conductivity tensor has inequivalent diagonal
components due to off-axis nodal positions which may be detectable in
experiments.Comment: 8 pages, 1 figur
Crystalline electric field effects in the electrical resistivity of PrOsSb
The temperature and magnetic field dependencies of the electrical
resistivity of the recently discovered heavy fermion superconductor
\PrOsSb{} have features that are associated with the splitting of the Pr
Hund's rule multiplet by the crystalline electric field (CEF). These features
are apparently due to magnetic exchange and aspherical Coulomb scattering from
the thermally populated CEF-split Pr energy levels. The data
in zero magnetic field can be described well by calculations based on CEF
theory for various ratios of magnetic exchange and aspherical Coulomb
scattering, and yield CEF parameters that are qualitatively consistent with
those previously derived from magnetic susceptibility, specific heat, and
inelastic neutron scattering measurements. Calculated isotherms for a
ground state qualitatively account for the `dome-shaped' feature
in the measured isotherms.Comment: 8 pages, 2 figures, submitted to Journal of Physics: Condensed Matte
Correlation between incoherent phase fluctuations and disorder in YPrBaCuO epitaxial films from Nernst effect measurements
Measurements of Nernst effect, resistivity and Hall angle on epitaxial films
of YPrBaCuO(Pr-YBCO, 00.4) are
reported over a broad range of temperature and magnetic field. While the Hall
and resistivity data suggest a broad pseudogap regime in accordance with
earlier results, these first measurements of the Nernst effect on Pr-YBCO show
a large signal above the superconducting transition temperature(T). This
effect is attributed to vortex-like excitations in the phase incoherent
condensate existing above T. A correlation between disorder and the width
of the phase fluctuation regime has been established for the YBCO family of
cuprates, which suggests a T110K for disorder-free
YBaCuO.Comment: 5 pages, 6 figure
Non-Fermi liquid behavior in a fluctuating valence system, the filled skutterudite compound CeRu_{4}As_{12}
Electrical resistivity , specific heat C, and magnetic susceptibility
measurements made on the filled skutterudite CeRu_4As_{12} reveal
non-Fermi liquid (NFL) T - dependences at low T, i.e., (T) T^{1.4}
and weak power law or logarithmic divergences in C(T)/T and (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
Superconductivity, magnetic order, and quadrupolar order in the filled skutterudite system PrNdOsSb
Superconductivity, magnetic order, and quadrupolar order have been
investigated in the filled skutterudite system
PrNdOsSb as a function of composition in magnetic
fields up to 9 tesla and at temperatures between 50 mK and 10 K. Electrical
resistivity measurements indicate that the high field ordered phase (HFOP),
which has been identified with antiferroquadruoplar order, persists to
0.5. The superconducting critical temperature of PrOsSb
is depressed linearly with Nd concentration to 0.55, whereas the
Curie temperature of NdOsSb is depressed linearly with Pr
composition to () 0.45. In the superconducting region, the upper
critical field is depressed quadratically with in the range 0
0.3, exhibits a kink at 0.3, and then
decreases linearly with in the range 0.3 0.6. The
behavior of appears to be due to pair breaking caused by the
applied magnetic field and the exhange field associated with the polarization
of the Nd magnetic moments, in the superconducting state. From magnetic
susceptibility measurements, the correlations between the Nd moments in the
superconducting state appear to change from ferromagnetic in the range 0.3
0.6 to antiferromagnetic in the range 0
0.3. Specific heat measurements on a sample with 0.45
indicate that magnetic order occurs in the superconducting state, as is also
inferred from the depression of with .Comment: 7 pages, 7 figures, currently submitted to Phys. Rev.
Observation of a temperature dependent electrical resistance minimum above the magnetic ordering temperature in GdPdSi
Results on electrical resistivity, magnetoresistance, magnetic Results on
electrical resistivity, magnetoresistance, magnetic susceptibility, heat
capacity and Gd Mossbauer measurements on a Gd-based intermetallic compound,
GdPdSi are reported. A finding of interest is that the resistivity
unexpectedly shows a well-defined minimum at about 45 K, well above the long
range magnetic ordering temperature (21 K), a feature which gets suppressed by
the application of a magnetic field. This observation in a Gd alloy presents an
interesting scenario. On the basis of our results, we propose electron
localization induced by s-f (or d-f) exchange interaction prior to long range
magnetic order as a mechanism for the electrical resistance minimum.Comment: 4 pages, 4 figure
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