Giant Magnetoresistance Effect in Grain-Type Alloy Thin Films: II -Annealing and Double-Layering-

An annealing study suggested that the internal diffusion and interfacial diffusion of Ag atoms in ferromagnetic FeCo grains made negative and positive contributions, respectively, to obtaining a large magnetoresistance (MR) ratio. The magnetic saturation field (H
s
) associated with MR characteristics decreased in proportion to the decrease in resistivity as the annealing temperature and/or annealing time increased. The coercive force in double-layered films with constant Co-Ag thickness decreased with increasing permalloy layer thickness. This indicates that the two layers are magnetically coupled. However, the H
s
was maintained to be extremely large. The MR ratio in the double-layered films was occasionally larger than that in a Co-Ag single layer.