EFFECTIVENESS OF ANTIFERROMAGNETIC OXIDE EXCHANGE FOR SANDWICH LAYERS

This study of Co50 angstrom/Cu(t)/Co50 angstrom sandwich films with large magnetoresistance (MR) emphasizes the function of a cobalt-oxide overlayer which exchange couples with the Co(50 angstrom) upper layer. By purposely adding a CoO layer consistency of magnetic properties which govern MR are observed. We find uniform MR properties for Cu(t) thicknesses from 10 to 60 angstrom. 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. We also discuss the possibilities that exchange coupling between the upper and lower Co(50 angstrom) layers exists.