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 (Hs) 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 Hs 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.