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Stm Studies of GMR Spin Valves

Published online by Cambridge University Press:  15 February 2011

R. D. K. Misra
Affiliation:
National Institute of Standards and Technology Gaithersburg, MD 20899
T. Ha
Affiliation:
National Institute of Standards and Technology Gaithersburg, MD 20899
Y. Kadmon
Affiliation:
National Institute of Standards and Technology Gaithersburg, MD 20899
C. J. Powell
Affiliation:
National Institute of Standards and Technology Gaithersburg, MD 20899
M. D. Stiles
Affiliation:
National Institute of Standards and Technology Gaithersburg, MD 20899
R. D. McMichael
Affiliation:
National Institute of Standards and Technology Gaithersburg, MD 20899
W. F. Egelhoff Jr
Affiliation:
National Institute of Standards and Technology Gaithersburg, MD 20899
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Abstract

We have investigated the surface roughness and the grain size in giant magnetoresistance (GMR) spin valve multilayers of the general type: FeMn/Ni80Fe20Co/Cu/Co/Ni80Fe20 on glass and aluminum oxide substrates by scanning tunneling microscopy (STM). The two substrates give very similar results. These polycrystalline GMR multilayers have a tendency to exhibit larger grain size and increased roughness with increasing thickness of the metal layers. Samples deposited at a low substrate temperature (150 K) exhibit smaller grains and less roughness. Valleys between the dome-shaped individual grainsare the dominant form of roughness. This roughness contributes to the ferromagnetic, magnetostatic coupling in these films, an effect termed “orange peel” coupling by Néel. We have calculated the strength of this coupling, based on our STM images, and obtain values generally within about 20% of the experimental values. It appears likely that the ferromagnetic coupling generally attributed to so-called “pinholes” in the Cu when the Cu film thickness is too small is actually “orange peel” coupling caused by these valleys.

Type
Research Article
Copyright
Copyright © Materials Research Society 1995

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References

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