Effectiveness of antiferromagnetic oxide exchange for sandwich layers

This study of Co50 Å/Cu(t)/Co50 Å sandwich films with large magnetoresistance (MR) is presented. Emphasis is placed on the function of a cobalt-oxide overlayer which exchanges couples with the Co(50 Å) upper layer. By purposely adding a CoO layer, the consistency of the magnetic properties which govern MR is observed. Uniform MR properties are found for Cu(t) thicknesses from 10 to 60 Å. The temperature dependence of MR, which is related to the antiferromagnetic transition temperature of the CoO, shows that MR becomes small at 180 K. The MR is absent when a metallic Cu overlayer is used instead of CoO. The possibilities that exchange coupling between the upper and lower Co(50 Å) layers exist are discussed