2,265 research outputs found
Two Dimensional Spin-Polarized Electron Gas at the Oxide Interfaces
The formation of a novel spin-polarized 2D electron gas at the LaMnO
monolayer embedded in SrMnO is predicted from the first-principles
density-functional calculations. The La (d) electrons become confined in the
direction normal to the interface in the potential well of the La layer,
serving as a positively-charged layer of electron donors. These electrons
mediate a ferromagnetic alignment of the Mn t spins near the interface
via the Anderson-Hasegawa double exchange and become, in turn, spin-polarized
due to the internal magnetic fields of the Mn moments.Comment: 5 pages, 6 figure
Anatomy of neck configuration in fission decay
The anatomy of neck configuration in the fission decay of Uranium and Thorium
isotopes is investigated in a microscopic study using Relativistic mean field
theory. The study includes and in the valley of stability
and exotic neutron rich isotopes , , , ,
, likely to play important role in the r-process
nucleosynthesis in stellar evolution. Following the static fission path, the
neck configurations are generated and their composition in terms of the number
of neutrons and protons are obtained showing the progressive rise in the
neutron component with the increase of mass number. Strong correlation between
the neutron multiplicity in the fission decay and the number of neutrons in the
neck is seen. The maximum neutron-proton ratio is about 5 for U and
Th suggestive of the break down of liquid-drop picture and inhibition
of the fission decay in still heavier isotopes. Neck as precursor of a new mode
of fission decay like multi-fragmentation fission may also be inferred from
this study.Comment: 16 pages, 5 figures (Accepted
Strain and Electric Field Modulation of the Electronic Structure of Bilayer Graphene
We study how the electronic structure of the bilayer graphene (BLG) is
changed by electric field and strain from {\it ab initio} density-functional
calculations using the LMTO and the LAPW methods. Both hexagonal and Bernal
stacked structures are considered. The BLG is a zero-gap semiconductor like the
isolated layer of graphene. We find that while strain alone does not produce a
gap in the BLG, an electric field does so in the Bernal structure but not in
the hexagonal structure. The topology of the bands leads to Dirac circles with
linear dispersion in the case of the hexagonally stacked BLG due to the
interpenetration of the Dirac cones, while for the Bernal stacking, the
dispersion is quadratic. The size of the Dirac circle increases with the
applied electric field, leading to an interesting way of controlling the Fermi
surface. The external electric field is screened due to polarization charges
between the layers, leading to a reduced size of the band gap and the Dirac
circle. The screening is substantial in both cases and diverges for the Bernal
structure for small fields as has been noted by earlier authors. As a biproduct
of this work, we present the tight-binding parameters for the free-standing
single layer graphene as obtained by fitting to the density-functional bands,
both with and without the slope constraint for the Dirac cone.Comment: 7 pages, 7 figure
Investigation of Complex Impedance and Modulus Properties of Nd Doped 0.5BiFeO3-0.5PbTiO3 Multiferroic Composites
0.5BiNdxFe1-xO3-0.5PbTiO3 (x=0.05, 0.10, 0.15, 0.20) composites were
successfully synthesized by a solid state reaction technique. At room
temperature X-ray diffraction shows tetragonal structure for all concentrations
of Nd doped 0.5BiFeO3-0.5PbTiO3 composites. The nature of Nyquist plot confirms
the presence of bulk effects only for all compositions of Nd-doped
0.5BiFeO3-0.5PbTiO3 composites. The bulk resistance is found to decreases with
the increasing in temperature as well as Nd concentration and exhibits a
typical negative temperature coefficient of resistance (NTCR) behavior. Both
the complex impedance and modulus studies have suggested the presence of
non-Debye type of relaxation in the materials. Conductivity spectra reveal the
presence of hopping mechanism in the electrical transport process of the
materials. The activation energy of the composite increases with increasing Nd
concentration and were found to be 0.28, 0.27, 0.31 and 0.32eV for x=0.05,
0.10, 0.15, 0.20 respectively at 200-275 oC for conduction process.Comment: 22 pages, 12 figures, 2 tables, 34 Referenc
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