NiO/CoFeB/Cu/CoFeB spin valves with B content of 0 to 10 at.% were prepared to
investigate the dependence of the giant magnetoresistance(GMR) effect on the thickness of free
magnetic layers. In the spin valves, GMR effects were observed even when the free magnetic layers
were very thin, 1 or even 0.5 nm. For lower B content, the magnetoresistance (MR) ratio rapidly
increased with the increase of free magnetic layer thickness, while for higher B content, the MR ratio
was maximum at the thickness roughly equal to the mean free path of electrons in the magnetic layers.
By using the Camley-Barnas model, the value of the MR ratio and the resistivity can be consistently
explained if the specular reflection of electrons is considered at the interface between magnetic and
nonmagnetic layers.
The effect of annealing on the oscillatory behavior of giant magnetoresistance (GMR) is studied in Co/Cu multilayers. Annealing at 200° C in vacuum reduces the height of the 1st peak of GMR oscillation significantly. However, the degradation of interface measured by X-ray diffraction is not large compared with the change in GMR.
Microscopic change of the interface state causes ferromagnetic interlayer coupling between adjacent Co layers and diminishes the 1st GMR peak. The 2nd GMR peak, on the other hand, is not so sensitive to the degradation of the interface.
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 fcc 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 bct structure.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.