10,571 research outputs found
Vortex dynamics and second magnetization peak in PrFeAsOF superconductor
We have studied the vortex dynamics in the PrFeAsOF
superconducting sample by dc magnetization and dynamic magnetization-relaxation
rate measurements. The field dependence of the superconducting
irreversible magnetization reveals a second magnetization peak or
fishtail effect. The large value of is an indication of moderate vortex
motion and relatively weak pinning energy. Data analysis based on the
generalized inversion scheme suggests that the vortex dynamics can be described
by the collective pinning model. The temperature dependence of the critical
current is consistent with the pinning due to the spatial variation in the mean
free path near a lattice defect ( pinning). The temperature and field
dependence of indicates a crossover from elastic to plastic vortex creep
with increasing temperature and magnetic field. Finally, we have constructed
the vortex phase diagram based on the present data.Comment: 11 pages, 8 Figures, Accepted for publication in Journal of Applied
Physic
Signatures of an invisibly decaying Higgs particles at LHC
The Higgs particle can decay dominantly into an invisible channel in the
Majoron models. We have explored the prospect of detecting such a Higgs
particle at LHC via its associated production with a gluon, Z or W boson. While
the signal/background ratio is too small for the first process, the latter two
provide viable signatures for detecting such a Higgs particle.Comment: (e-mail: [email protected]) LaTex; No. of pages 12, no. of
figures 3 (available on request
Fe-spin reorientation in PrFeAsO : Evidences from resistivity and specific heat studies
We report the magnetic field dependence of resistivity () and specific
heat () for the non-superconducting PrFeAsO compound. Our study shows a
hitherto unobserved anomaly at in the resistivity and specific heat
data which arises as a result of the interplay of antiferromagnetic (AFM) Pr
and Fe sublattices. Below the AFM transition temperature (), Pr
moment orders along the crystallographic c axis and its effect on the iron
subsystem causes a reorientation of the ordered inplane Fe moments in a
direction out of the plane. Application of magnetic field introduces
disorder in the AFM Pr sublattice, which, in turn, reduces the out-of-plane
Pr-Fe exchange interaction responsible for Fe spin reorientation. Both in
() and curves, the peak at broadens with the
increase of due to the introduction of the disorder in the AFM Pr
sublattice by magnetic field. In () curve, the peak shifts towards
lower temperature with and disappears above 6 T while in curve
the peak remains visible up to 14 T. The broadening of the anomaly at
in with increasing further confirms that magnetic
field induces disorder in the AFM Pr sublattice.Comment: 8 pages, 10 Figure
An R-Parity Breaking SUSY Solution to the and ALEPH Anomalies
We discuss an optimal -parity breaking SUSY solution to the excess as well as the ALEPH 4-jet anomaly. The latter arises from the pair production of stop via chargino decay at LEP1.5, followed by its --violating decay into a light quark pair. The model satisfies top quark and --boson decay constraints along with gaugino mass unification
Quantm Magnetoresistance of the PrFeAsO oxypnictides
We report the observation of an unusual dependence of transverse
magnetoresistance (MR) in the PrFeAsO, one of the parent compound of pnictide
superconductors. Below the spin density wave transition, MR is large, positive
and increases with decreasing temperature. At low temperatures, MR increases
linearly with up to 14 T. For 40 K, MR vs curve develops a
weak curvature in the low-field region which indicates a crossover from
linear to dependence as 0. The linear MR originates
from the Dirac cone states and has been explained by the quantum mechanical
model proposed by Abrikosov.Comment: accepted for publication in Appl. Phys. Let
Development of high efficiency solar cells on silicon web
Web base material is being improved with a goal toward obtaining solar cell efficiencies in excess of 18% (AM1). Carrier loss mechanisms in web silicon was investigated, techniques were developed to reduce carrier recombination in the web, and web cells were fabricated using effective surface passivation. The effect of stress on web cell performance was also investigated
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