1,261 research outputs found
The Electromigration Force in Metallic Bulk
The voltage induced driving force on a migrating atom in a metallic system is
discussed in the perspective of the Hellmann-Feynman force concept, local
screening concepts and the linear-response approach. Since the force operator
is well defined in quantum mechanics it appears to be only confusing to refer
to the Hellmann-Feynman theorem in the context of electromigration. Local
screening concepts are shown to be mainly of historical value. The physics
involved is completely represented in ab initio local density treatments of
dilute alloys and the implementation does not require additional precautions
about screening, being typical for jellium treatments. The linear-response
approach is shown to be a reliable guide in deciding about the two
contributions to the driving force, the direct force and the wind force.
Results are given for the wind valence for electromigration in a number of FCC
and BCC metals, calculated using an {\it ab initio} KKR-Green's function
description of a dilute alloy.Comment: 14 pages, 1 Postscript figur
Characteristics of RF-sputtered CoCr films
The magnetization of the CoCr recording medium has been investigated by several methods. First the perpendicular hysteresis loops are analysed in the thickness range from 500 to 20,000 Ã…. This provided evidence that the magnetization process is typefied by domain wall motion. Second the dependence of the coercivity on the film thickness has been determined. The dependence found can be explained if it is assumed, that the coercivity is caused by domain walls, impeded by the crystallite boundaries. Finally stand-still recording experiments have been performed, which confirm that magnetization takes place by the displacement of domain walls. The switching criterion in the writing process is best met by taking the field averaged over the film thickness
Design of a dual patch multielement radiant cooler, phase 1 Final report, 16 Feb. - 16 Jul. 1970
Dual patch multi-element radiant cooler for earth oriented spacecraf
The construction and test of a dual patch multi-element radiant cooler Quarterly report, 17 Sep. - 17 Dec. 1970
Design and performance testing of dual patch multi-element radiant cooler with cold tra
Construction and test of a dual patch multi-element radiant cooler
Design, construction, and test of dual patch multi-element radiant coole
Resistivity due to low-symmetrical defects in metals
The impurity resistivity, also known as the residual resistivity, is
calculated ab initio using multiple-scattering theory. The mean-free path is
calculated by solving the Boltzmann equation iteratively. The resistivity due
to low-symmetrical defects, such as an impurity-vacancy pair, is calculated for
the FCC host metals Al and Ag and the BCC transition metal V. Commonly, 1/f
noise is attributed to the motion of such defects in a diffusion process.Comment: 24 pages in REVTEX-preprint format, 10 Postscript figures. Phys. Rev.
B, vol. 57 (1998), accepted for publicatio
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