Interface characterization and thermal stability of Co/Al-O/CoFe spin-dependent tunnel junctions

A detailed study of the interface properties as well as the thermal stability has been done for the Co/Al-O/CoFe/NiFe magnetic tunnel junction, by using high resolution transmission electron microscopy equipped with energy dispersive x-ray spectrum. The Al behaves more stable against thermal annealing compared with the Fe, Co, Ni, and O elements. The reduction of the tunnel magnetoresistance ratio for the low annealing temperature (200 degreesC) may be caused by the spin flip scattering at oxide ion, rather than by the change in magnetic properties. The annealing at higher temperatures (300 degreesC and 400 degreesC) results in a strong interdiffusion, and in turn the disappearance of the magnetoresistance due to the shortcut of the junction. (C) 2002 American Institute of Physics.