1,089 research outputs found
Microwave properties of : Influence of magnetic scattering
We report measurements of the surface impedance of
, . Increasing
concentration leads to some striking results not observed in samples doped
by non-magnetic constituents. The three principal features of the data
- multiple structure in the transition, a high residual resistance and, at high
concentrations, an upturn of the low data, are all characteristic of
the influence of magnetic scattering on superconductivity, and appear to be
common to materials where magnetism and superconductivity coexist. The low
behavior of appears to change from to at large
doping, and provides evidence of the influence of magnetic pairbreaking of the
.Comment: 5 pages, 3 eps figures, Revtex, 2-column format, uses graphicx. To
appear in Physica C. Postscript version also available at
http://sagar.physics.neu.edu/preprints.htm
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
Anomalous Paramagnetic Magnetization in Mixed State of CeCoIn single crystals
Magnetization and torque measurements were performed on CeCoIn single
crystals to study the mixed-state thermodynamics. These measurements allow the
determination of both paramagnetic and vortex responses in the mixed-state
magnetization. The paramagnetic magnetization is suppressed in the mixed state
with the spin susceptibility increasing with increasing magnetic field. The
dependence of spin susceptibility on magnetic field is due to the fact that
heavy electrons contribute both to superconductivity and paramagnetism and a
large Zeeman effect exists in this system. No anomaly in the vortex response
was found within the investigated temperature and field range
Nonlinear paramagnetic magnetization in the mixed state of CeCoIn_5
Torque and magnetization measurements in magnetic fields up to 14 T were
performed on CeCoIn single crystals. The amplitude of the paramagnetic
torque shows an dependence in the mixed state and an
dependence in the normal state. In addition, the mixed-state magnetizations for
both and axes show anomalous behavior after the
subtraction of the corresponding paramagnetic contributions as linear
extrapolations of the normal-state magnetization. These experimental results
point towards a nonlinear paramagnetic magnetization in the mixed state of
CeCoIn, which is a result of the fact that both orbital and Pauli limiting
effects dominate in the mixed state.Comment: 2 pages, 2 figures, conferenc
Pairing Symmetry of CeCoIn Detected by In-plane Torque Measurements
In-plane torque measurements were performed on heavy fermion CeCoIn
single crystals in the temperature range 1.8 K K and
applied magnetic field up to 14 T. The normal-state torque is given by
. The reversible part of the
mixed-state torque, obtained after subtracting the corresponding normal state
torque, shows also a four-fold symmetry. In addition, sharp peaks are present
in the irreversible torque at angles of 4, 3/4, 5/4, 7/4,
etc. Both the four-fold symmetry in the reversible torque and the sharp peaks
in the irreversible torque of the mixed state imply symmetry of the
superconducting order parameter. The field and temperature dependences of the
reversible mixed-state torque provide further evidence for wave
symmetry. The four-fold symmetry in the normal state has a different origin
since it has different field and temperature dependences than the one in the
mixed state. The possible reasons of the normal state four-fold symmetry are
discussed
Signatures of pressure induced superconductivity in insulating Bi2212
We have performed several high pressure electrical resistance experiments on
Bi1.98Sr2.06Y0.68Cu2O8, an insulating parent compound of the high-Tc Bi2212
family of copper oxide superconductors. We find a resistive anomaly, a downturn
at low temperature, that onsets with applied pressure in the 20-40 kbar range.
Through both resistance and magnetoresistance measurements, we identify this
anomaly as a signature of induced superconductivity. Resistance to higher
pressures decreases Tc, giving a maximum of 10 K. The higher pressure
measurements exhibit a strong sensitivity to the hydrostaticity of the pressure
environment. We make comparisons to the pressure induced superconductivity now
ubiquitous in the iron arsenides.Comment: 5 pages, 4 figures, submitted to Phys. Rev.
Strong magnetic fluctuations in superconducting state of CeCoIn
We show results on the vortex core dissipation through current-voltage
measurements under applied pressure and magnetic field in the superconducting
phase of CeCoIn. We find that as soon as the system becomes
superconducting, the vortex core resistivity increases sharply as the
temperature and magnetic field decrease. The sharp increase in flux flow
resistivity is due to quasiparticle scattering on critical antiferromagnetic
fluctuations. The strength of magnetic fluctuations below the superconducting
transition suggests that magnetism is complimentary to superconductivity and
therefore must be considered in order to fully account for the low-temperature
properties of CeCoIn.Comment: 7 pages, 6 figure
Evidence for a common physical description of non-Fermi-liquid behavior in f-electron systems
The non-Fermi-liquid (NFL) behavior observed in the low temperature specific
heat and magnetic susceptibility of f-electron systems is
analyzed within the context of a recently developed theory based on Griffiths
singularities. Measurements of and in the systems
, , and (M = Pd,
Pt) are found to be consistent with predicted by this model with in the NFL regime.
These results suggest that the NFL properties observed in a wide variety of
f-electron systems can be described within the context of a common physical
picture.Comment: 4 pages, 4 figure
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