237 research outputs found
Interpreting Quantum Chromodynamics from Spin Glass- and Polymer Analogies
In an informal way some kind of Ising Lattice QCD is introduced which allows
to interprete and discuss the well-known theory of quantum chromodynamics
(confinement, quarks and gluons, etc.) from simple phenomena of magnetism and
polymer physics. Also the viewpoint of duality is stressed. Moreover, the
non-abelian character of the Lie group SU(3) is important. The essential
arguments for confinement and asymptotic freedom are given at the very end of
the manuscript, after an appendix.Comment: 6 pages; 0 figures, the main arguments are given at the end of an
appendi
CPP- Giant Magnetoresistance and Thermo-Electric Power of multilayers
Oscillations of magnetoresistance and thermo-electric power (TEP) vs. both
nonmagnetic spacer as well as ferromagnetic slab thicknesses are studied in the
current-perpendicular-to-plane (CPP) geometry, in terms of a single-band
tight-binding model. The spin-dependent conductance has been calculated from
the Kubo formula by means of a recursion Green's function technique, and the directly from the well-known Onsager relations.
In general, the observed oscillations may have either just one or two
periods. In the latter case the long period of oscillations, related to
spectacular beats, is apparently of non-RKKY type.
The relative TEP oscillations are strongly enhanced in comparison with those
of the giant magnetoresistance, have the same periods, but different phases and
a negative bias.Comment: Latex (4 pages); 2 figures included; to appear in Proc. of 'Physics
of Magn. 1996', Acta Physica Polonic
Ab-initio-calculations of the GMR-effect in Fe/V multilayers
In a self-consistent semi-empirical numerical approach based on
ab-initio-calculations for small samples, we evaluate the GMR effect for
disordered (001)-(3--Fe/3--V) multilayers by means of a Kubo
formalism. We consider four different types of disorder arrangements: In case
(i) and (ii), the disorder consists in the random interchange of some Fe and V
atoms, respectively, at interface layers; in case (iii) in the formation of
small groups of three substitutional Fe atoms in a V interface layer and a
similar V group in a Fe layer at a different interface; and for case (iv) in
the substitution of some V atoms in the innermost V layers by Fe. For cases (i)
and (ii), depending on the distribution of the impurities, the GMR effect is
enhanced or reduced by increasing disorder, in case (iii) the GMR effect is
highest, whereas finally, in case (iv), a negative GMR is obtained (''inverse
GMR'').Comment: LaTex, 30 pages, including 16 drawings; to appear in JMM
Dynamics of ferromagnetic nanomagnets with vortex or single-domain configuration
We study the dynamics of flat circular permalloy nanomagnets for 1.) magnetic
vortex and 2.) single-domain configurations, using micromagnetic simulation.
Dynamical studies for isolated vortex structures show that both the vorticity
and the central polarity of the out-of-plane component can be switched fast
(50-100 ps) and independently. Micromagnetic simulations of the switching
process in thin cylindrical Permalloy (Py) nanoparticles with an initial stable
single-domain state show nearly homogeneous single-domain behaviour followed by
excitation of spin waves.Comment: 2 pages with 3 eps-figures, --> ICM2003 Rome 28.7.-1.8.03, --> JMM
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