GMR effect across the transition from multilayer to granular structure

We have studied the evolution of giant magnetoresistance in magnetic multilayers obtained by alternately growing thin cobalt and copper layers having proportional thickness. Co nominal layers thickness was progressively reduced from 12 A down to 2 A. This decrease produces a fragmentation of the Co layers and the evolution of samples magnetic properties indicates a transition from multilayer to granular behavior. Magnetic and magnetoresistive data of the granular phase have been analyzed as a function of Co thickness in order to determine particle size distribution.