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Proceedings Paper

Spin injection into superconductors
Author(s): Michael S. Osofsky; Robert J. Soulen Jr.; J. M. Byers; B. F. Woodfield; Douglas B. Chrisey; James S. Horwitz; Raymond C. Y. Auyeung
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Paper Abstract

The effect of spin-polarized injection on the superconductivity order parameter is investigated in a device consisting of YBa2Cu3O7-(delta )/Au/Ni0.8Fe0.2 layers. A non-equilibrium theory which qualitatively agrees with the results of measurements made on superconductor/insulator/ferromagnet structures is presented. A quantitative analysis shows that this theory predicts injection currents that are several orders of magnitude too large. Recent results suggest that superconductivity in thin films can be strongly influenced by the injection of a spin- polarized current from a ferromagnetic material. The effect has been found to occur in both low Tc (Sn) and high Tc (YBa2Cu3O7-(delta )) superconductors when either a conventional ferromagnetic metal, permalloy (Ni0.8Fe0.2), or a colossal magnetoresistive material were used as the source of spin polarization. Control experiments showed that unpolarized current from a nonmagnetic metal had comparatively little effect on the same superconductors. A phenomenological model, in which the energy gap of the superconductor is perturbed by the presence of excess spin polarized electrons, has been shown to qualitatively mimic the experimental results. However, an estimate of the current needed to significantly suppress the gap is shown to be several orders of magnitude larger than is observed.

Paper Details

Date Published: 22 December 1998
PDF: 6 pages
Proc. SPIE 3481, Superconducting and Related Oxides: Physics and Nanoengineering III, (22 December 1998); doi: 10.1117/12.335914
Show Author Affiliations
Michael S. Osofsky, Naval Research Lab. (United States)
Robert J. Soulen Jr., Naval Research Lab. (United States)
J. M. Byers, Naval Research Lab. and George Washington Univ. (United States)
B. F. Woodfield, Naval Research Lab. (United States)
Douglas B. Chrisey, Naval Research Lab. (United States)
James S. Horwitz, Naval Research Lab. (United States)
Raymond C. Y. Auyeung, SFA, Inc. (United States)

Published in SPIE Proceedings Vol. 3481:
Superconducting and Related Oxides: Physics and Nanoengineering III
Davor Pavuna; Ivan Bozovic, Editor(s)

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