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American Institute of Physics, Applied Physics Letters, 23(98), p. 232506

DOI: 10.1063/1.3597224

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Enhanced magnetoresistance in naturally oxidized MgO-based magnetic tunnel junctions with ferromagnetic CoFe/CoFeB bilayers

Journal article published in 2011 by D. K. Schreiber, Y.-S. Choi, Yuzi Z. Liu ORCID, Ann N. Chiaramonti ORCID, David N. Seidman, A. K. Petford Long
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This paper is available in a repository.

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Abstract

Three-dimensional elemental distributions in magnetic tunnel junctions containing naturally oxidized MgO tunnel barriers are characterized using atom-probe tomography. Replacing the CoFeB free layer (reference layer) with a CoFe/CoFeB (CoFeB/CoFe) bilayer increases the magnetoresistance from 105% to 192% and decreases the resistance-area product from 14.5 to 3.4 Ω μm2. The CoFe/CoFeB bilayer improves the compositional uniformity within the free layer by nucleating CoFeB crystals across the entire layer, resulting in a homogeneous barrier/free layer interface. In contrast, the simple CoFeB free layer partially crystallizes with composition differences from grain to grain (5–30 nm), degrading the tunnel junction performance.