6,108 research outputs found
On the Coexistence Magnetism/Superconductivity in the Heavy-Fermion Superconductor CePtSi
The interplay between magnetism and superconductivity in the newly discovered
heavy-fermion superconductor CePtSi has been investigated using the
zero-field SR technique. The SR data indicate that the whole muon
ensemble senses spontaneous internal fields in the magnetic phase,
demonstrating that magnetism occurs in the whole sample volume. This points to
a microscopic coexistence between magnetism and heavy-fermion
superconductivity.Comment: Final version, new figure structure, references correcte
Evidence for Cooper Pair Diffraction on the Vortex Lattice of Superconducting Niobium
We investigated the Abrikosov vortex lattice (VL) of a pure Niobium single
crystal with the muon spin rotation (\mu SR) technique. Analysis of the \mu SR
data in the framework of the BCS-Gor'kov theory allowed us to determine
microscopic parameters and the limitations of the theory. With decreasing
temperature the field variation around the vortex cores deviates substantially
from the predictions of the Ginzburg-Landau theory and adopts a pronounced
conical shape. This is evidence of partial diffraction of Cooper pairs on the
VL predicted by Delrieu for clean superconductors.Comment: 9 pages, 6 figure
'White knuckle care work' : violence, gender and new public management in the voluntary sector
Drawing on comparative data from Canada and Scotland, this article explores reasons why violence is tolerated in non-profit care settings. This article will provide insights into how workers' orientations to work, the desire to care and the intrinsic rewards from working in a non-profit context interact with the organization of work and managerially constructed workplace norms and cultures (Burawoy, 1979) to offset the tensions in an environment characterized by scarce resources and poor working conditions. This article will also outline how the same environment of scarce resources causes strains in management's efforts to establish such cultures. Working with highly excluded service users with problems that do not respond to easy interventions, workers find themselves working at the edge of their endurance, hanging on by their fingernails, and beginning to participate in various forms of resistance; suggesting that even among the most highly committed, 'white knuckle care' may be unsustainable
Evidence for spin liquid ground state in SrDyO frustrated magnet probed by muSR
Muon spin relaxation (SR) measurements were carried out on
SrDyO, a frustrated magnet featuring short range magnetic correlations
at low temperatures. Zero-field muon spin depolarization measurements
demonstrate that fast magnetic fluctuations are present from K down to
20 mK. The coexistence of short range magnetic correlations and fluctuations at
mK indicates that SrDyO features a spin liquid ground state.
Large longitudinal fields affect weakly the muon spin depolarization, also
suggesting the presence of fast fluctuations. For a longitudinal field of
T, a non-relaxing asymmetry contribution appears below K,
indicating considerable slowing down of the magnetic fluctuations as
field-induced magnetically-ordered phases are approached.Comment: 6 pages, 4 figures, to be published as a proceeding of HFM2016 in
Journal of Physics: Conference Series (JPCS
Magnetic field distribution and characteristic fields of the vortex lattice for a clean superconducting niobium sample in an external field applied along a three-fold axis
The field distribution in the vortex lattice of a pure niobium single crystal
with an external field applied along a three-fold axis has been investigated by
the transverse-field muon-spin-rotation (TF-SR) technique over a wide
range of temperatures and fields. The experimental data have been analyzed with
the Delrieu's solution for the form factor supplemented by phenomenological
formulas for the parameters. This has enabled us to experimentally establish
the temperatures and fields for the Delrieu's, Ginzburg-Landau's, and Klein's
regions of the vortex lattice. Using the numerical solution of the
quasiclassical Eilenberger's equation the experimental results have been
reasonably understood. They should apply to all clean BCS superconductors. The
analytical Delrieu's model supplemented by phenomenological formulas for its
parameters is found to be reliable for analyzing TF-SR experimental data
for a substantial part of the mixed phase. The Abrikosov's limit is contained
in it.Comment: 12 pages, 15 figure
Sub-milliarcsecond precision spectro-astrometry of Be stars
The origin of the disks around Be stars is still not known. Further progress
requires a proper parametrization of their structure, both spatially and
kinematically. This is challenging as the disks are very small. Here we assess
whether a novel method is capable of providing these data. We obtained spectro
astrometry around the Pa beta line of two bright Be stars, alpha Col and zeta
Tau, to search for disk signatures. The data, with a pixel to pixel precision
of the centroid position of 0.3..0.4 milliarcsecond is the most accurate such
data to date. Artefacts at the 0.85 mas level are present in the data, but
these are readily identified as they were non-repeatable in our redundant
datasets. This does illustrate the need of taking multiple data to avoid
spurious detections. The data are compared with simple model simulations of the
spectro astrometric signatures due to rotating disks around Be stars. The upper
limits we find for the disk radii correspond to disk sizes of a few dozen
stellar radii if they rotate Keplerian. This is very close to observationally
measured and theoretically expected disk sizes, and this paper therefore
demonstrates that spectro-astrometry, of which we present the first such
attempt, has the potential to resolve the disks around Be stars.Comment: 6 pages, A&A accepte
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