X-ray reflectivity analysis of giant-magnetoresistance spin-valve layered structures

The amount of intermixing at the interfaces of sputter-deposited spin-valve layered structures, comprising Si/Ta (50 Å)/NiFe (75 Å)/Cu (22.5 Å)/NiFe (50 Å)/FeMn (110 Å)/Ta (50 Å), were obtained from least-squares refinement of x-ray reflectivity data. The observations were modeled by layers of nominal composition with compositional inhomogeneity at the interfaces. Layer thicknesses deduced from x-ray analysis were generally within a few percent of the nominal values. Interface widths between the two NiFe layers and the Cu spacer were 6.2-7.4 Å, indicating intermixing of atoms of about three monolayers at the interfaces. A 10.0-Å interface width was found at the FeMn interface suggesting a mixed-phase layer of α- and γ-FeMn. Layer densities, except those of the less dense Ta underlayer and the oxidized Ta surface, agreed to within 10% of bulk values. The results were in agreement with those obtained from closely related Si/Ta/NiFe/Cu/NiFe/Ta, Si/Ta/NiFe/Cu/Ta, Si/Ta/NiFe/Ta, and Si/Ta films.