Magnetoresistance in Ferromagnetic Tunnel Junctions with Oxidized Al Layers.

Ferromagnetic tunnel junctions with oxidized Al layers were prepared by electron-beam (EB) evaporation and dc magnetron sputtering (SP). The tunneling magnetoresistance (TMR) ratio observed in an EB-Co/Al(5.0 nm)-oxide/EB-Fe sample was around 3%. When the first ferromagnetic layer was fabricated by sputtering, the measured TMR ratio increased to 10% and the Al thickness at the maximum TMR ratio shifted to a thinner one. According to the results of surface observation with an atomic force microscope (AFM), the surface morphology of the first ferromagnetic layer strongly influenced the oxidized Al layer, and the smooth surface of the first ferromagnetic layer increased the TMR ratio.