185 research outputs found
Small-Angle Neutron Scattering and Magnetization Study of HoNi2B2C
The superconducting and magnetic properties of HoNi2B2C single crystals are
investigated through transport, magnetometry and small-angle neutron scattering
measurements. In the magnetic phases that enter below the superconducting
critical temperature, the small-angle neutron scattering data uncover networks
of magnetic surfaces. These likely originate from uncompensated moments e.g. at
domain walls pinned to crystallographic grain boundaries. The field and
temperature dependent behaviour appears consistent with the metamagnetic
transitions reported in earlier works.Comment: 11 pages , 4 figures, submitted to Low Temperature Physic
The role of secondary Reggeons in central meson production
We estimate the contribution of f_2 trajectory exchange to the central \eta
and \eta^\prime production. It is shown that secondary Reggeons may give a
large contribution to processes of double diffractive meson production at high
energy.Comment: 7 pages, Latex, 5 figure
Vortex studies in superconducting Ba(Fe0.93Co0.07)2As2
We present small-angle neutron scattering (SANS) and Bitter decoration
studies of the superconducting vortices in
Ba(FeCo)As}. A highly disordered vortex configuration
is observed at all measured fields, and is attributed to strong pinning. This
conclusion is supported by the absence of a Meissner rim in decoration images
obtained close to the sample edge. The field dependence of the magnitude of the
SANS scattering vector indicates vortex lattice domains of (distorted)
hexagonal symmetry, consistent with the decoration images which show primarily
6-fold coordinated vortex domains. An analysis of the scattered intensity shows
that this decreases much more rapidly than expected from estimates of the upper
critical field, consistent with the large degree of disorder.Comment: 5 pages, 4 figure
GCIP water and energy budget synthesis (WEBS)
As part of the World Climate Research Program\u27s (WCRPs) Global Energy and Water-Cycle Experiment (GEWEX) Continental-scale International Project (GCIP), a preliminary water and energy budget synthesis (WEBS) was developed for the period 1996–1999 from the “best available” observations and models. Besides this summary paper, a companion CD-ROM with more extensive discussion, figures, tables, and raw data is available to the interested researcher from the GEWEX project office, the GAPP project office, or the first author. An updated online version of the CD-ROM is also available at http://ecpc.ucsd.edu/gcip/webs.htm/. Observations cannot adequately characterize or “close” budgets since too many fundamental processes are missing. Models that properly represent the many complicated atmospheric and near-surface interactions are also required. This preliminary synthesis therefore included a representative global general circulation model, regional climate model, and a macroscale hydrologic model as well as a global reanalysis and a regional analysis. By the qualitative agreement among the models and available observations, it did appear that we now qualitatively understand water and energy budgets of the Mississippi River Basin. However, there is still much quantitative uncertainty. In that regard, there did appear to be a clear advantage to using a regional analysis over a global analysis or a regional simulation over a global simulation to describe the Mississippi River Basin water and energy budgets. There also appeared to be some advantage to using a macroscale hydrologic model for at least the surface water budgets
The effect of the noncentral impurity-matrix interaction upon the thermal expansion and polyamorphism of solid CO-C60 solutions at low temperatures
Orientational glasses with CO molecules occupying 26% and 90% of the
octahedral interstitial sites in the C60 lattice have been investigated by the
dilatometric method in a temperature interval of 2.5 - 23 K. At temperatures 4
- 6 K the glasses undergo a first-order phase transition which is evident from
the hysteresis of the thermal expansion and the maxima in the temperature
dependences of the linear thermal expansion coefficients, and the
thermalization times of the samples. The effect of the noncentral CO-C60
interaction upon the thermal expansion and the phase transition in these
glasses was clarified by comparing the behavior of the properties of the CO-C60
and N2-C60 solutions.Comment: 11 pages, 7 figure
Observation of the magnetic domain structures in CuNi thin films at low temperatures
We report on the first experimental visualization of domain structure in
films of weakly ferromagnetic CuNi alloy with different
thickness at liquid helium temperatures. Improved high-resolution Bitter
decoration technique was used to map the magnetic contrast on the top of the
films well below the Curie temperature T ( 60 K). In contrast
to magnetic force microscopy, this technique allowed visualization of the
domain structure without its disturbance while the larger areas of the sample
were probed. Maze-like domain patterns, typical for perpendicular magnetic
anisotropy, were observed. The average domain width was found to be about 100
nm.Comment: 4 pages, 5 figures, will be published in JETP Let
MICRODISC GEL ELECTROPHORESIS IN SODIUM DODECYL SULFATE OF ORGANIC MATERIAL FROM RAT OTOCONIAL COMPLEXES *
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74849/1/j.1749-6632.1981.tb30921.x.pd
Effect of electron irradiation on vortex dynamics in YBa_2Cu_3O_{7-x} single crystals
We report on drastic change of vortex dynamics with increase of quenched
disorder: for rather weak disorder we found a single vortex creep regime, which
we attribute to a Bragg-glass phase, while for enhanced disorder we found an
increase of both the depinning current and activation energy with magnetic
field, which we attribute to entangled vortex phase. We also found that
introduction of additional defects always increases the depinning current, but
it increases activation energy only for elastic vortex creep, while it
decreases activation energy for plastic vortex creep.Comment: 4 pages, 3 figures, submited to Phys. Rev.
The effect of the noncentral impurity-matrix interaction upon the thermal expansion and polyamorphism of solid CO–C₆₀ solutions at low temperatures
Orientational glasses with CO molecules occupying 26 and 90% of the octahedral interstitial sites in the
C₆₀ lattice have been investigated by the dilatometric method in a temperature interval of 2.5–22 K. At temperatures
4–6 K the glasses undergo a first-order phase transition which is evident from the hysteresis of the
thermal expansion and the maxima in the temperature dependences of the linear thermal expansion coefficients
α (T), and the thermalization times τ₁(T) of the samples. The effect of the noncentral CO–C₆₀ interaction
upon the thermal expansion and the phase transition in these glasses was clarified by comparing the behavior
of the properties of the CO–C₆₀ and N₂–C₆₀ solutions
Impurity Effect on the In-plane Penetration Depth of the Organic Superconductors -(BEDT-TTF) ( = Cu(NCS) and Cu[N(CN)]Br)
We report the in-plane penetration depth of single
crystals -(BEDT-TTF) ( Cu(NCS) and Cu[N(CN)]Br) by
means of the reversible magnetization measurements under the control of
cooling-rate. In = Cu(NCS), as an
extrapolation toward = 0 K does not change by the cooling-rate within the
experimental accuracy, while is slightly reduced. On the other
hand, in = Cu[N(CN)]Br, indicates a distinct
increase by cooling faster. The different behavior of
on cooling-rate between the two salts is quantitatively explained in terms of
the local-clean approximation (London model), considering that the former salt
belongs to the very clean system and the later the moderate clean one. The good
agreement with this model demonstrates that disorders of ethylene-group in
BEDT-TTF introduced by cooling faster increase the
electron(quasiparticle)-scattering, resulting in shorter mean free path.Comment: 8 pages, 9 figure
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