Direct observation of the barrier asymmetry in magnetic tunnel junctions

Koller, P. H. P.; Swagten, H. J. M.; De Jonge, W. J. M.; Boeve, H.; Coehoorn, R.
June 2004
Applied Physics Letters;6/14/2004, Vol. 84 Issue 24, p4929
Academic Journal
A photoconductance method has been used to study directly the barrier asymmetry in TaOx magnetic tunnel junctions. Due to optical electron-hole pair generation in the barrier itself and subsequent transport in the electric field, the sign and magnitude of the barrier asymmetry can be determined quite accurately. The reliability of the technique is demonstrated by the independence on the direction of illumination. The oxidation time where the asymmetry becomes zero is found to coincide with a maximum in the magnetoresistance ratio. This is argued to be due to the complete oxidation of the barrier material, resulting in a symmetric tunnel barrier. © 2004 American Institute of Physics.


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