1,145 research outputs found
Magnetic fluctuations and effective magnetic moments in \gamma-iron due to electronic structure peculiarities
Applying the local density and dynamical mean field approximations to
paramagnetic \gamma-iron we revisit the problem of theoretical description of
magnetic properties in a wide temperature range. We show that contrary to
\alpha-iron, the frequency dependence of the electronic self-energy has a
quasiparticle form for both, t_{2g} and e_g states. In the temperature range
T=1200-1500 K, where \gamma-iron exist in nature, this substance can be
nevertheless characterized by temperature-dependent effective local moments,
which yield relatively narrow peaks in the real part of the local magnetic
susceptibility. At the same time, at low temperatures \gamma-iron (which is
realized in precipitates) is better described in terms of itinerant picture. In
particular, the nesting features of the Fermi surfaces yield maximum of the
static magnetic susceptibility at the incommensurate wave vector q_{max}
belonging the direction q_X-q_W (q_X=(2\pi/a)(1,0,0),q_W=(2\pi/a)(1,1/2,0), a
is a lattice parameter) in agreement with the experimental data. This state is
found however to compete closely with the states characterized by magnetic wave
vectors along the directions q_X-q_L-q_K, where q_L=(2\pi/a)(1/2,1/2,1/2),
q_K=(2\pi/a)(3/4,3/4,0). From the analysis of the uniform magnetic
susceptibility we find that contrary to \alpha-iron, the Curie-Weiss law is not
fulfilled in a broad temperature range, although the inverse susceptibility is
nearly linear in the moderate-temperature region (1200-1500 K). The
non-linearity of the inverse uniform magnetic susceptibility in a broader
temperature range is due to the density of states peak located close to the
Fermi level. The effective exchange integrals in the paramagnetic phase are
estimated on the base of momentum dependent susceptibility.Comment: 10 pages, 11 figure
Sivers effect in Drell Yan at RHIC
On the basis of a fit to the Sivers effect in deep-inelastic scattering, we
make predictions for single-spin asymmetries in the Drell-Yan process at RHIC.Comment: 10 pages, 7 figures, 1 table. v2: References and comments added,
minor correction
Study of correlation of production and decay planes in diffractive dissociation process on nuclei
A large correlation of production and decay planes of
(\pi^-\pi^+\pi^-)-system in dissociation of -beam 40 GeV/c on nuclear
targets was observed. The dependence of the correlation on atomic number,
Feynmann variable and transversal momentum as well as on invariant mass of the
pion triple and neutral pion pair were investigated. It was shown that the
phenomenon has a clear dynamic origin and resembles the single spin asymmetry
behavior.Comment: 8 pages, latex epsfig.sty, 5 eps figures. Submitted to Yad. Fiz
Transverse momentum dependent distribution functions in a covariant parton model approach with quark orbital motion
Transverse parton momentum dependent distribution functions (TMDs) of the
nucleon are studied in a covariant model, which describes the intrinsic motion
of partons in terms of a covariant momentum distribution. The consistency of
the approach is demonstrated, and model relations among TMDs are studied. As a
byproduct it is shown how the approach allows to formulate the non-relativistic
limit.Comment: 16 page
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