Interface composition in magnetic tunnel junctions

The magnetoresistance of magnetic tunnel junctions critically depends on th e exact composition at the interfaces. As such the completeness of the oxid ation process of the Al layer (used to produce Al2O3-based tunnel junctions ) plays an essential role in the magnetoresistance. We studied the chemical properties of ferromagnet/Al2O3 interfaces as a function of original Al la yer thickness. We have studied the concentrations of elementary and oxidize d Al, Co, Ni, and Fe for varying roughness of the ferromagnetic layer. The oxidation process critically depends on the roughness of the underlying fer romagnetic (FM) layer. Al layers grown onto smooth FM layers oxidize homoge neously whereas Al layers grown on rough FM layers show a complicated oxida tion behavior. Within the sensitivity of the analysis technique, we did not observe oxidation of the ferromagnetic layers, even for the overoxidized p art of the samples. (C) 2001 American Institute of Physics.