Annealing time dependence of structural and magnetotransport properties of Ni81Fe19 (2 nm)/Ag (4 nm) multilayers

Granular films of Ni81Fe19 nanoparticles embedded in a non-magnetic Ag matrix were prepared, after annealing the as cast multilayers, and the evolution of the structural and magnetotransport properties as a function of annealing time were investigated. The as cast films exhibit negligible isotropic magnetoresistance and upon annealing grain boundary diffusion occurs resulting in the appearance of giant magnetoresistance (GMR) effect. Stagnation of grain growth and significant residual values of GMR for prolonged annealing times occur due to retarding forces on grain boundary movement. X-ray refinement analysis indicates incoherent growth of Ni81Fe19 and Ag. A phenomenological model was use to fit the GMR curve as a function of the reduced magnetization.