Bulk contribution to magneto-resistance In Co-based magnetic tunnel junction

In this paper, we will present evidence in magnetic tunnel junctions (MTJ) with Co electrode to show bulk contribution. In the experiment, a wedge-shaped Co layer was inserted between the barrier and bottom electrode in a perfectly oxidized NiFe/AlO/NiFe MTJ. We observed slow saturation of TMR values with the increasing thickness of Co. After carefully excluding structure related possibility by time of flight secondary in mass spectroscopy measurement, this slow saturation can only be explained by the existence of bulk contribution in MTJ. We also observed this tunneling characteristic length decreases with the increase of applied bias.