Effect of Buffer Layer Texture on the Crystallization of CoFeB and on the Tunnel Magnetoresistance in MgO Based Magnetic Tunnel Junctions

Two different buffer layers (Ta/Ru/Ta and thick Ta) were tested for MgO MTJs. The influence of buffer layer texture on the crystallization of CoFeB bottom and top electrodes and on the tunnel magnetoresistance effect was investigated. X-ray results suggest that, after anneal, the CoFeB layer above M...

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Bibliographic Details
Published in:IEEE transactions on magnetics 2009-10, Vol.45 (10), p.3464-3466
Main Authors: Cao, J., Kanak, J., Stobiecki, T., Wisniowski, P., Freitas, P.P.
Format: Article
Language:English
Subjects:
Amorphous magnetic materials
Buffer layer
Buffer layers
Cross-disciplinary physics: materials science
rheology
Crystallization
Electrodes
Electronic equipment testing
Exact sciences and technology
Glass
Iron
Magnesium oxide
magnetic tunnel junctions
Magnetic tunneling
Magnetism
Materials science
Orientation
Other topics in materials science
Physics
Solar energy
Sputtering
Surface layer
Tantalum
Texture
Tunnel magnetoresistance
Tunneling magnetoresistance
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Summary:Two different buffer layers (Ta/Ru/Ta and thick Ta) were tested for MgO MTJs. The influence of buffer layer texture on the crystallization of CoFeB bottom and top electrodes and on the tunnel magnetoresistance effect was investigated. X-ray results suggest that, after anneal, the CoFeB layer above MgO is well (200) textured and it does not depend on the buffer layer since MgO (100) barrier supplies a good template for CoFeB (200) orientation, while the crystallization of bottom CoFeB layer relies on the buffer layer texture. Different from Ta (110) found in Ta/Ru/Ta buffer layer, a thick Ta buffer layer has beta-(200) texture, which induces (001) oriented grains in MnPt layer. Because of the epitaxy relationship between MnPt and FeCo with MnPt(001)[100]//FeCo(200)[110], MnPt (001) oriented grains lead to the crystallization of bottom CoFeB layer with (200) orientation. As a result, higher TMR ratio up to 290% was achieved in the EB-MTJs with thick Ta buffer layer.
ISSN:0018-9464
1941-0069
DOI:10.1109/TMAG.2009.2025382