36,433 research outputs found
Influence of Domain Wall on Magnetocaloric Effect in GdPt
The resistivity, magnetoresistance and in-field heat capacity measurements
were performed on GdPt intermetallic compound. The magnetocaloric
parameters and were derived from the in-field heat
capacity data. Comparison has been made between the magnetocaloric effect
and difference in resistivity
as a function of temperature. There is distinct difference in the temperature
dependence of and below the ferromagnetic transition
temperature. However after removing the domain wall contribution from , the nature of and dependence as a function of
temperature are similar. Our observation indicates that the domain wall
contribution in magnetocaloric effect is negligible in spite of the fact that
it has significant contribution in magnetotransport.Comment: RevTex 4 pages, 6 figure
Transport properties of diluted magnetic semiconductors: Dynamical mean field theory and Boltzmann theory
The transport properties of diluted magnetic semiconductors (DMS) are
calculated using dynamical mean field theory (DMFT) and Boltzmann transport
theory. Within DMFT we study the density of states and the dc-resistivity,
which are strongly parameter dependent such as temperature, doping, density of
the carriers, and the strength of the carrier-local impurity spin exchange
coupling. Characteristic qualitative features are found distinguishing weak,
intermediate, and strong carrier-spin coupling and allowing quantitative
determination of important parameters defining the underlying ferromagnetic
mechanism. We find that spin-disorder scattering, formation of bound state, and
the population of the minority spin band are all operational in DMFT in
different parameter range. We also develop a complementary Boltzmann transport
theory for scattering by screened ionized impurities. The difference in the
screening properties between paramagnetic () and ferromagnetic ()
states gives rise to the temperature dependence (increase or decrease) of
resistivity, depending on the carrier density, as the system goes from the
paramagnetic phase to the ferromagnetic phase. The metallic behavior below
for optimally doped DMS samples can be explained in the Boltzmann theory
by temperature dependent screening and thermal change of carrier spin
polarization.Comment: 15 pages, 15 figure
Muon anomaly and a lower bound on higgs mass due to a light stabilized radion in the Randall-Sundrum model
We investigate the Randall-Sundrum model with a light stabilized radion
(required to fix the size of the extra dimension) in the light of muon
anomalous magnetic moment . Using the recent data
(obtained from the E821 experiment of the BNL collaboration) which differs by
from the Standard Model result, we obtain constraints on radion
mass \mphi and radion vev \vphi. In the presence of a radion the beta
functions \beta(\l) and of higgs quartic coupling (\l) and
top-Yukawa coupling () gets modified. We find these modified beta
functions. Using these beta functions together with the anomaly constrained
\mphi and \vphi, we obtain lower bound on higgs mass . We compare our
result with the present LEP2 bound on .Comment: Version to be appeared in IJMP
Supernovae as Probes of Extra Dimensions
Since the dawn of the new millennium, there has been a revived interest in
the concept of extra dimensions.In this scenario all the standard model matter
and gauge fields are confined to the 4 dimensions and only gravity can escape
to higher dimensions of the universe.This idea can be tested using table-top
experiments, collider experiments, astrophysical or cosmological observations.
The main astrophysical constraints come from the cooling rate of supernovae,
neutron stars, red giants and the sun. In this article, we consider the energy
loss mechanism of SN1987A and study the constraints it places on the number and
size of extra dimensions and the higher dimensional Planck scale.Comment: 5 pages, no figures, new references are adde
A competing order scenario of two-gap behavior in hole doped cuprates
Angle-dependent studies of the gap function provide evidence for the
coexistence of two distinct gaps in hole doped cuprates, where the gap near the
nodal direction scales with the superconducting transition temperature ,
while that in the antinodal direction scales with the pseudogap temperature. We
present model calculations which show that most of the characteristic features
observed in the recent angle-resolved photoemission spectroscopy (ARPES) as
well as scanning tunneling microscopy (STM) two-gap studies are consistent with
a scenario in which the pseudogap has a non-superconducting origin in a
competing phase. Our analysis indicates that, near optimal doping,
superconductivity can quench the competing order at low temperatures, and that
some of the key differences observed between the STM and ARPES results can give
insight into the superlattice symmetry of the competing order.Comment: 9 pages, 7 fig
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