Annealing of Ni80Fe20/Cu and Co/Cu multilayers

Ni80Fe20/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 degrees 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 degrees 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 degrees C. Moreover, in some cases even an improvement of GMR upon the annealing procedure may be found. (C) 2000 American Institute of Physics. [S0021-8979(00)58008-6].