391 research outputs found
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
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
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
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
Fermi Surface Reconstruction in CeRhCoIn
The evolution of the Fermi surface of CeRhCoIn was studied as
a function of Co concentration via measurements of the de Haas-van Alphen
effect. By measuring the angular dependence of quantum oscillation frequencies,
we identify a Fermi surface sheet with -electron character which undergoes
an abrupt change in topology as is varied. Surprisingly, this
reconstruction does not occur at the quantum critical concentration ,
where antiferromagnetism is suppressed to T=0. Instead we establish that this
sudden change occurs well below , at the concentration x ~ 0.4 where long
range magnetic order alters its character and superconductivity appears. Across
all concentrations, the cyclotron effective mass of this sheet does not
diverge, suggesting that critical behavior is not exhibited equally on all
parts of the Fermi surface.Comment: 4 pages, 4 figure
Scaling Behavior of Angular Dependent Resistivity in CeCoIn: Possible Evidence for d-Wave Density Waves
In-plane angular dependent resistivity ADR was measured in the non-Fermi
liquid regime of CeCoIn single crystals at temperatures K and in
magnetic fields up to 14 T. Two scaling behaviors were identified in low
field region where resistivity shows T-linear dependence, separated by a
critical angle which is determined by the anisotropy of
CeCoIn; i.e., ADR depends only on the perpendicular (parallel) field
component below (above) . These scaling behaviors and other salient
features of ADR are consistent with d-wave density waves
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
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