477 research outputs found
Proton-induced magnetic order in carbon: SQUID measurements
In this work we have studied systematically the changes in the magnetic
behavior of highly oriented pyrolytic graphite (HOPG) samples after proton
irradiation in the MeV energy range. Superconducting quantum interferometer
device (SQUID) results obtained from samples with thousands of localized spots
of micrometer size as well on samples irradiated with a broad beam confirm
previously reported results. Both, the para- and ferromagnetic contributions
depend strongly on the irradiation details. The results indicate that the
magnetic moment at saturation of spots of micrometer size is of the order of
emu.Comment: Invited contribution at ICACS2006 to be published in Nucl. Instr. and
Meth. B. 8 pages and 6 figure
Vortex Lattice Depinning vs. Vortex Lattice Melting: a pinning-based explanation of the equilibrium magnetization jump
In this communication we argue that the Vortex Lattice Melting scenario fails
to explain several key experimental results published in the literature. From a
careful analysis of these results we conclude that the Flux Line Lattice (FLL)
does not melt along a material- and sample-dependent boundary but the
opposite, it de-couples from the superconducting matrix becoming more ordered.
When the FLL depinning is sharp, the difference between the equilibrium
magnetization of the pinned and unpinned FLL leads to the
observed step-like change . We demonstrate that the
experimentally obtained can be well accounted for by a
variation of the pinning efficiency of vortices along the boundary.Comment: 8 pages, 1 Figur
Influence of temperature on the nodal properties of the longitudinal thermal conductivity of YBaCuO
The angle dependence at different temperatures of the longitudinal thermal
conductivity in the presence of a planar magnetic field
is presented. In order to study the influence of the gap symmetry on the
thermal transport angular scans were measured up to a few Kelvin below the
critical temperature . We found that the four-fold oscillation of
vanishes at K and transforms into a one-fold
oscillation with maximum conductivity for a field of 8 T applied parallel to
the heat current. Nevertheless, the results indicate that the d-wave pairing
symmetry is the main pairing symmetry of the order parameter up to .
Numerical results of the thermal conductivity using an Andreev reflection model
for the scattering of quasiparticles by supercurrents under the assumption of
d-wave symmetry provide a semiquantitative description of the overall results.Comment: 7 figures, EPJ B (in press, 2003
The Labusch Parameter of a Driven Flux Line Lattice in YBaCuO Superconducting Films
We have investigated the influence of a driving force on the elastic coupling
(Labusch parameter) of the field-cooled state of the flux line lattice (FLL) in
400 nm thick YBaCuO superconducting films. We found that the FLL of
a field-cooled state without driving forces is not in an equilibrium state.
Results obtained for magnetic fields applied at and 30
relative to CuO planes, show an enhancement of the elastic coupling of the
films at driving current densities several orders of magnitude smaller than the
critical one. Our results indicate that the FLL appears to be in a relatively
ordered, metastable state after field cooling without driving forces.Comment: 4 Figure
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