Structural and magnetoresistance studies in granular (Ni81Fe19,Ni80Co20)/Ag synthesized from annealed multilayers

The structural and magnetotransport properties have been studied in (Ni81Fe19,Ni80Co20)/Ag granular alloy films synthesized by the annealing of sputtered multilayers containing ultrathin magnetic layers. The magnetic concentration, particle size, and morphology of the precipitates can be controlled by adjusting the magnetic layer thickness during the deposition process. Magnetoresistance as large as 30% was found at 4.2 K with a rather small saturation field (<2 kOe), leading to relatively high field sensitivity. Magnetoresistance and saturation field in these alloy films essentially depend on the magnetic precipitate size, concentration, and annealing temperature. The temperature dependence of magnetization and magnetoresistance was also studied, and the correlations among the microstructure, magnetotransport, and magnetic properties are discussed.