6,058 research outputs found
Evaluation of the optical conductivity tensor in terms of contour integrations
For the case of finite life-time broadening the standard Kubo-formula for the
optical conductivity tensor is rederived in terms of Green's functions by using
contour integrations, whereby finite temperatures are accounted for by using
the Fermi-Dirac distribution function. For zero life-time broadening, the
present formalism is related to expressions well-known in the literature.
Numerical aspects of how to calculate the corresponding contour integrals are
also outlined.Comment: 8 pages, Latex + 2 figure (Encapsulated Postscript
Reorientation phase transitions in thin magnetic films: a review of the classical vector spin model within the mean field approach
The ground state and the finite temperature phase diagrams with respect to
magnetic configurations are studied systematically for thin magnetic films in
terms of a classical Heisenberg model including magnetic dipole-dipole
interaction and uniaxial anisotropy. Simple relations are derived for the
occurrence of the various phase boundaries between the different regions of the
magnetic orientations. In particular, the range of the first and second order
reorientation phase transitions are determined for bi- and trilayers.Comment: 23 pages, LaTeX + 7 figures (Encapsulated PostScript), submitted to
Philosophical Magazine B (Feb. 28, 2001
Electrical transport properties of bulk NiFe alloys and related spin-valve systems
Within the Kubo-Greenwood formalism we use the fully relativistic,
spin-polarized, screened Korringa-Kohn-Rostoker method together with the
coherent-potential approximation for layered systems to calculate the
resistivity for the permalloy series NiFe. We are able to
reproduce the variation of the resistivity across the entire series; notably
the discontinuous behavior in the vicinity of the structural phase transition
from bcc to fcc. The absolute values for the resistivity are within a factor of
two of the experimental data. Also the giant magnetoresistance of a series of
permalloy-based spin-valve structures is estimated; we are able to reproduce
the trends and values observed on prototypical spin-valve structures.Comment: 6 pages, ReVTeX + 4 figures (Encapsulated Postscript), submitted to
PR
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