3,984 research outputs found
Effects of Core-Hole Screening on Spin-Polarised Auger Spectra from Ferromagnetic Nickel
We calculate the spin- and temperature-dependent local density of states for
ferromagnetic Ni in the presence of a core hole at a distinguished site in the
lattice. Correlations among the valence electrons and between valence and core
electrons are described within a multi-band Hubbard model which is treated by
means of second-order perturbation theory around the Hartree-Fock solution. The
core-hole potential causes strong screening effects in the Ni valence band. The
local magnetic moment is found to be decreased by a factor 5-6. The
consequences for the spin polarisation of CVV Auger electrons are discussed.Comment: LaTeX, 4 pages, 1 eps figure included, Acta Physica Polonica A (in
press), Physics of Magnetism '99 (Poznan, Poland
Momentum space evolution of chiral three-nucleon forces
A framework to evolve three-nucleon (3N) forces in a plane-wave basis with
the Similarity Renormalization Group (SRG) is presented and applied to
consistent interactions derived from chiral effective field theory at
next-to-next-to-leading order (NLO). We demonstrate the unitarity of the
SRG transformation, show the decoupling of low and high momenta, and present
the first investigation of universality in chiral 3N forces at low resolution
scales. The momentum-space-evolved 3N forces are consistent and can be directly
combined with the standard SRG-evolved two-nucleon (NN) interactions for
ab-initio calculations of nuclear structure and reactions.Comment: 5 pages, 4 figure
Fundamental Plane Distances to Early-type Field Galaxies in the South Equatorial Strip. I. The Spectroscopic Data
Radial velocities and central velocity dispersions are derived for 238 E/S0
galaxies from medium-resolution spectroscopy. New spectroscopic data have been
obtained as part of a study of the Fundamental Plane distances and peculiar
motions of early-type galaxies in three selected directions of the South
Equatorial Strip, undertaken in order to investigate the reality of large-scale
streaming motion; results of this study have been reported in M\"uller
(1998). The new APM South Equatorial Strip Catalog () was used to select the sample of field galaxies in
three directions: (1) 15h10 - 16h10; (2) 20h30 - 21h50; (3) 00h10 - 01h30. The
spectra obtained have a median S/N per of 23, an instrumental
resolution (FWHM) of 4 , and the spectrograph resolution
(dispersion) is 100 km~s. The Fourier cross-correlation method
was used to derive the radial velocities and velocity dispersions. The velocity
dispersions have been corrected for the size of the aperture and for the galaxy
effective radius. Comparisons of the derived radial velocities with data from
the literature show that our values are accurate to 40 km~s. A
comparison with results from J\orgensen et al. (1995) shows that the derived
central velocity dispersion have an rms scatter of 0.036 in .
There is no offset relative to the velocity dispersions of Davies et al.
(1987).Comment: accepted for publication in Astronomy & Astrophysics Supplement
Serie
Sensing Noncollinear Magnetism at the Atomic Scale Combining Magnetic Exchange and Spin-Polarized Imaging
Storing and accessing information in atomic-scale magnets requires magnetic
imaging techniques with single-atom resolution. Here, we show simultaneous
detection of the spin-polarization and exchange force, with or without the flow
of current, with a new method, which combines scanning tunneling microscopy and
non-contact atomic force microscopy. To demonstrate the application of this new
method, we characterize the prototypical nano-skyrmion lattice formed on a
monolayer of Fe/Ir(111). We resolve the square magnetic lattice by employing
magnetic exchange force microscopy, demonstrating its applicability to
non-collinear magnetic structures, for the first time. Utilizing
distance-dependent force and current spectroscopy, we quantify the exchange
forces in comparison to the spin-polarization. For strongly spin-polarized
tips, we distinguish different signs of the exchange force which we suggest
arises from a change in exchange mechanisms between the probe and a skyrmion.
This new approach may enable both non-perturbative readout combined with
writing by current-driven reversal of atomic-scale magnets
Experimental investigation of ultrahigh vacuum adhesion as related to the lunar surface Quarterly progress report, 1 Apr. - 31 Jun. 1969
Electrical charge distribution in ultrahigh vacuum fracture and etching of silicates for lunar simulation studie
Similarity Renormalization Group for Nucleon-Nucleon Interactions
The similarity renormalization group (SRG) is based on unitary
transformations that suppress off-diagonal matrix elements, forcing the
hamiltonian towards a band-diagonal form. A simple SRG transformation applied
to nucleon-nucleon interactions leads to greatly improved convergence
properties while preserving observables, and provides a method to consistently
evolve many-body potentials and other operators.Comment: 5 pages, 6 figures (8 figure files); references updated and
acknowledgment adde
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