56 research outputs found
Vortex lattice studies in CeCoIn5 with H perpendicular to c
We present small angle neutron scattering studies of the vortex lattice (VL)
in CeCoIn5 with magnetic fields applied parallel (H) to the antinodal [100] and
nodal [110] directions. For H || [100], a single VL orientation is observed,
while a 90 degree reorientation transition is found for H || [110]. For both
field orientations and VL configurations we find a distorted hexagonal VL with
an anisotropy, Gamma = 2.0 +/- 0.05. The VL form factor shows strong Pauli
paramagnetic effects similar to what have previously been reported for H ||
[001]. At high fields, above which the upper critical field (Hc2) becomes a
first-order transition, an increased disordering of the VL is observed.Comment: 5 pages, 4 figure
Observations of Pauli Paramagnetic Effects on the Flux Line Lattice in CeCoIn5
From small-angle neutron scattering studies of the flux line lattice (FLL) in
CeCoIn5, with magnetic field applied parallel to the crystal c-axis, we obtain
the field- and temperature-dependence of the FLL form factor, which is a
measure of the spatial variation of the field in the mixed state. We extend our
earlier work [A.D. Bianchi et al. 2008 Science 319, 177] to temperatures up to
1250 mK. Over the entire temperature range, paramagnetism in the flux line
cores results in an increase of the form factor with field. Near H_c2 the form
factor decreases again, and our results indicate that this fall-off extends
outside the proposed FFLO region. Instead, we attribute the decrease to a
paramagnetic suppression of Cooper pairing. At higher temperatures, a gradual
crossover towards more conventional mixed state behavior is observed.Comment: Submitted to New Journal of Physics, 13 pages, 4 figure
Antiferromagnetic ordering in a 90 K copper oxide superconductor
Using elastic neutron scattering, we evidence a commensurate
antiferromagnetic Cu(2) order (AF) in the superconducting (SC) high-
cuprate (y=0.013, =93 K). As
in the Co-free system, the spin excitation spectrum is dominated by a magnetic
resonance peak at 41 meV but with a reduced spectral weight. The substitution
of Co thus leads to a state where AF and SC cohabit showing that the CuO
plane is a highly antiferromagnetically polarizable medium even for a sample
where T remains optimum.Comment: 3 figure
In situ uniaxial pressure cell for x-ray and neutron scattering experiments
We present an in situ uniaxial pressure device optimized for small angle x-ray and neutron scattering experiments at low-temperatures and high magnetic fields. A stepper motor generates force, which is transmitted to the sample via a rod with an integrated transducer that continuously monitors the force. The device has been designed to generate forces up to 200 N in both compressive and tensile configurations, and a feedback control allows operating the system in a continuous-pressure mode as the temperature is changed. The uniaxial pressure device can be used for various instruments and multiple cryostats through simple and exchangeable adapters. It is compatible with multiple sample holders, which can be easily changed depending on the sample properties and the desired experiment and allow rapid sample changes
In situ uniaxial pressure cell for x-ray and neutron scattering experiments
We present an in situ uniaxial pressure device optimized for small angle x-ray and neutron scattering experiments at low-temperatures and high magnetic fields. A stepper motor generates force, which is transmitted to the sample via a rod with an integrated transducer that continuously monitors the force. The device has been designed to generate forces up to 200 N in both compressive and tensile configurations, and a feedback control allows operating the system in a continuous-pressure mode as the temperature is changed. The uniaxial pressure device can be used for various instruments and multiple cryostats through simple and exchangeable adapters. It is compatible with multiple sample holders, which can be easily changed depending on the sample properties and the desired experiment and allow rapid sample changes
Local structure study about Co in YBa(CuCo)O thin films using polarized XAFS
We have studied the local structure around Co in
YBa(CuCo)O thin films with three different
concentrations: x=0.07, 0.10, 0.17, and in a
PrBa(CuCo)O thin film of concentration x=0.05
using the X-ray Absorption Fine Structure (XAFS) technique. Data were collected
at the Co -edge with polarizations both parallel and perpendicular to the
film surface. We find that the oxygen neighbors are well ordered and shortened
in comparison with YBCO Cu-O values to 1.80 \AA{} and 1.87 \AA{} in the
-axis and -plane, respectively. A comparison of further neighbors in the
thin film and powder data show that these peaks in the film are suppressed in
amplitude relative to the powder samples, which suggests there is more disorder
and/or distortions of the Co environment present in the thin films.Comment: 14 pages; To be submitted to Phys. Rev.
High Pressure Effects on Superconductivity
The review is devoted to a discussion of the effects of high pressure imposed
on superconducting materials. Low-temperature superconductors, high-temperature
superconducting cuprates, and some unconventional superconducting compounds are
investigated. Experimental as well as theoretical results regarding the
pressure effects on Tc and other interesting properties are summarized.Comment: To be published in: "Frontiers in Superconducting Materials", Edt. A.
Narlikar, Springer Verla
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