2,473 research outputs found
Linear-in-frequency optical conductivity in GdPtBi due to transitions near the triple points
The complex optical conductivity of the half-Heusler compound GdPtBi is
measured in a frequency range from 20 to 22 000 cm (2.5 meV - 2.73 eV)
at temperatures down to 10 K in zero magnetic field. We find the real part of
the conductivity, , to be almost perfectly linear in
frequency over a broad range from 50 to 800 cm ( 6 - 100 meV) for
K. This linearity strongly suggests the presence of
three-dimensional linear electronic bands with band crossings (nodes) near the
chemical potential. Band-structure calculations show the presence of triple
points, where one doubly degenerate and one nondegenerate band cross each other
in close vicinity of the chemical potential. From a comparison of our data with
the optical conductivity computed from the band structure, we conclude that the
observed nearly linear originates as a cumulative effect
from all the transitions near the triple points.Comment: 5+ pages, 5 figures, band-structure and optical-conductivity
calculations adde
Two-channel conduction in YbPtBi
We investigated transport, magnetotransport, and broadband optical properties
of the half-Heusler compound YbPtBi. Hall measurements evidence two types of
charge carriers: highly mobile electrons with a temperature-dependent
concentration and low-mobile holes; their concentration stays almost constant
within the investigated temperature range from 2.5 to 300 K. The optical
spectra (10 meV - 2.7 eV) can be naturally decomposed into contributions from
intra- and interband absorption processes, the former manifesting themselves as
two Drude bands with very different scattering rates, corresponding to the
charges with different mobilities. These results of the optical measurements
allow us to separate the contributions from electrons and holes to the total
conductivity and to implement a two-channel-conduction model for description of
the magnetotransport data. In this approach, the electron and hole mobilities
are found to be around 50000 and 10 cm/Vs at the lowest temperatures (2.5
K), respectively.Comment: 6 page
Large zero-field cooled exchange-bias in bulk Mn2PtGa
We report a large exchange-bias (EB) effect after zero-field cooling the new
tetragonal Heusler compound Mn2PtGa from the paramagnetic state. The
first-principle calculation and the magnetic measurements reveal that Mn2PtGa
orders ferrimagnetically with some ferromagnetic (FM) inclusions. We show that
ferrimagnetic (FI) ordering is essential to isothermally induce the exchange
anisotropy needed for the zero-field cooled (ZFC) EB during the virgin
magnetization process. The complex magnetic behavior at low temperatures is
characterized by the coexistence of a field induced irreversible magnetic
behavior and a spin-glass-like phase. The field induced irreversibility
originates from an unusual first-order FI to antiferromagnetic transition,
whereas, the spin-glass like state forms due to the existence of anti-site
disorder intrinsic to the material.Comment: 5 pages, 4 figures, supplementary material included in a separate
file; accepted for publication in PR
Spin-lattice coupling mediated giant magnetodielectricity across the spin reorientation in Ca2FeCoO5
The structural, phonon, magnetic, dielectric, and magneto dielectric
responses of the pure bulk Brownmillerite compound Ca2FeCoO5 are reported. This
compound showed giant magneto dielectric response (10%-24%) induced by strong
spin-lattice coupling across its spin reorientation transition (150-250 K). The
role of two Debye temperatures pertaining to differently coordinated sites in
the dielectric relaxations is established. The positive giant
magneto-dielectricity is shown to be a direct consequence of the modulations in
the lattice degrees of freedom through applied external field across the spin
reorientation transition. Our study illustrates novel control of
magneto-dielectricity by tuning the spin reorientation transition in a material
that possess strong spin lattice coupling.Comment: 7 pages, 12 figure
Large nonlinear absorption and refraction coefficients of carbon nanotubes estimated from femtosecond Z-scan measurements
Nonlinear transmission of 80 and 140 femtosecond pulsed light with wavelength through single walled carbon nanotubes suspended in water
containing sodium dodecyl sulphate is studied. Pulse-width independent
saturation absorption and negative cubic nonlinearity are observed,
respectively, in open and closed aperture Z-scan experiments. The theoretical
expressions derived to analyze the z-dependent transmission in the saturable
limit require two photon absorption coefficient and a
nonlinear index to fit the data.Comment: 10 pages, 2 figures. Accepted and to appear in Applied Physics
Letter
Extractive Titrimetric Determination of Hg(II), Cu(II) & Ag(I) Using Lead Diethyldithiocarbamate
636-63
Sustained drug release from multi-layered sequentially crosslinked electrospun gelatin nanofiber mesh
The aim of this study is to develop electrospun gelatin nanofibers based drug delivery carrier to achieve controlled and sustainable release of hydrophobic drug (piperine) for prolonged time. To accomplish this, we devised some strategies such as sandwiching the drug loaded gelatin nanofiber mesh with another gelatin nanofiber matrix without drug (acting as diffusion barrier), sequential crosslinking and finally, a combination of both. As fabricated multilayered electrospun nanofibers mesh was first characterized in terms of degradation study, morphology, drug-polymer interactions, thermal stability followed by studying their release kinetics in different physiological pH as per the gastrointestinal tract. Our results show that with optimized diffusional barrier support and sequential crosslinking together, a zero order sustained drug release up to 48 h may be achieved with a flexibility to vary the drug loading as per the therapeutic requirements. This work lays out the possibility of systematic design of multilayer nano-fiber mesh of a biopolymer as a drug delivery vehicle for hydrophobic drugs with a desired signature of zero order release for prolonged duration
- …