Structure and giant magnetoresistance effect of Fe/Cu and FeCoNi/Cu multilayers

We have studied the giant magnetoresistance (GMR) effect and the film structure of Fe/Cu and FeCoNi/Cu multilayers (MLs), where the FeCoNi alloy is in the composition range of the bcc phase. Both MLs show the oscillation of MR ratio similar to each other as a function of the Cu layer thickness. The phase of oscillation is much different from those in Co/Cu and fcc-FeCoNi/Cu MLs. The maximum MR ratios of 6% and 40% were obtained at 77 K, respectively, for (Fe 1.5 nm/Cu 1.4 nm)(20) and (Fe56CO30N14 1.5 nm/Cu 1.4 nm)(20) MLs. The EXAFS of the Cu K edge as well as the XRD pattern indicates that the structure of the Cu layers changes from bcc-like to fee phase as their thickness increases. At the Cu thickness of 1.5 nm, the Cu layers, in both MLs, are highly disordered and seem to have a bet structure. (C) 1997 American Institute of Physics.