  The maximum current-perpendicular-to-plane giant magnetoresistance is
searched for in magnetic multilayers made of Co, Ni, and Cu with disorder
levels similar to those found in room temperature experiments. The calculation
is made possible by a highly optimized linear response code, which uses the
impurity averaged Green's function technique and a 9-band per spin tight
binding model. Using simulated annealing, hundreds of different configurations
of the atomic layers are examined to find a maximum GMR of 450% in ultrathin
Ni/Cu superlattices.
