Anomalous tunneling magnetoresistance in junctions with an Au dusting layer at the Co/Al2O3 interface

Abstract

We report an anomalous magnetotransport in a magnetic tunnel junction (MTJ) containing an Au dusting layer with Au thickness 0.6 nm at the Co/Al2O3 interface, where the Co layer is pinned by the underlying FeMn layer. Despite its structure being exchange biased, the junction with the 0.6 nm Au layer exhibits symmetric magnetoresistance (MR) for both the applied magnetic field (H) directions, which is a typical MR feature without a pinning effect, and a low resistance state near Happroximate to0 Oe. It is also found that the same MR features, i.e., symmetric MR and a low resistance state near Happroximate to0 Oe, can be achieved in the MTJ without an Au insertion layer when the pinned Co moments are at an angle to the applied H direction. Based on measurements of the angular dependence of MR, we surmise that the anomalous MR is due to the effect of spin disorder in the Co layer, induced by the deposited Au layer. It is not likely that the anomalous effect is due to the quantum well state in the An layer. (C) 2003 American Institute of Physics.