EVOLUTION OF STRUCTURE AND MAGNETORESISTANCE IN GRANULAR NI(FE,CO)/AG MULTILAYERS - DEPENDENCE ON MAGNETIC LAYER THICKNESS

Structural and magnetoresistance results on annealed sputtered (Ni 81Fe19, Ni66Fe16Co18)/Ag granular multilayers are presented. Structural evolution has shown that highly (111) textured, discontinuous layered structures can persist on annealing up to 400°C. The average magnetic particle size is controlled by the annealing temperature and the initial magnetic layer thickness. No giant magnetoresistance was observed in the as-deposited films, while significant MR was found after annealing between 300°C and 400°C. Magnetoresistance over 30%, together with a small saturation field, was found at 4.2 K for a starting magnetic thickness of 4 Å. Increasing the magnetic layer thickness to 20 Å greatly improves the magnetic thermal stability, and leads to high magnetoresistive sensitivities of up to 0.35%/Oe in a field of 10 Oe at room temperature. The magnetization hysteresis, anisotropy, and magnetic interaction in such a granular multilayer are also discussed.