Annealing of Ni80Fe20/Cu and Co/Cu multilayers

Ni 80 Fe 20 /Cu and Co/Cu multilayers with Cu layer thicknesses corresponding to the first and second antiferromagnetic (afm) coupling maximum were prepared by dc-magnetron sputtering and investigated with respect to their annealing behavior. The as-deposited films showed giant magnetoresistance (GMR) up to 50% at room temperature. The annealing behavior of the multilayers belonging to the same Cu layer thickness is found to be very similar up to 200 °C. For both kind of multilayers with a Cu layer thickness of about 1 nm (first afm maximum) the GMR degrades upon annealing in excess of 140 °C. However, with a Cu layer thickness of about 2 nm (second afm maximum) the multilayers are stable with respect to their GMR properties even after prolonged exposure up to 200 °C. Moreover, in some cases even an improvement of GMR upon the annealing procedure may be found.