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 °C) 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 °C and 400 °C) results in a strong interdiffusion, and in turn the disappearance of the magnetoresistance due to the shortcut of the junction.