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Author Oepts, W. ♦ Gillies, M. F. ♦ Coehoorn, R. ♦ van de Veerdonk, R. J. M. ♦ de Jonge, W. J. M.
Sponsorship (US)
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Publisher The American Physical Society
Language English
Subject Keyword CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS ♦ MAGNETORESISTANCE ♦ OXIDATION ♦ PHYSICS ♦ PLASMA
Abstract Recently it has been observed that the magnetoresistance (MR) of plasma oxidized exchange biased Co/Al{sub 2}O{sub 3}/Co tunnel junctions can have a strongly asymmetric bias voltage (V{sub bias}) dependence. In this article we report on the dependence of this phenomenon on barrier oxidation time t{sub ox}. For junctions based on 1.5 nm Al, t{sub ox} was varied from 20 to 120 s. For t{sub ox}=20 s, for which the MR is approximately 20% at V{sub bias}=0, and for t{sub ox}{ge}90 s symmetric MR(V{sub bias}) curves are found, with the MR decreasing monotonically with {vert_bar}V{sub bias}{vert_bar}. A strong asymmetric bias voltage dependence was observed for intermediate oxidation times, which correspond to essentially full oxidation of the Al layer, but almost no formation of stoichiometric CoO at the bottom electrode. Samples with t{sub ox}=60 s show even an asymmetric double peak in MR(V{sub bias}). Due to its strength, it has an important consequence for device applications: for a series of junctions with variable t{sub ox} the maximum signal voltage (at a fixed current) is not necessarily obtained for junctions which have the largest MR ratio at V{sub bias}=0. {copyright} 2001 American Institute of Physics.
ISSN 00218979
Educational Use Research
Learning Resource Type Article
Publisher Date 2001-06-15
Publisher Place United States
Journal Journal of Applied Physics
Volume Number 89
Issue Number 12


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