Interfacial-roughness effects on giant magnetoresistance and interlayer coupling in Co/Cu superlattices

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Abstract
Giant magnetoresistance and interlayer exchange coupling in Co/Cu superlattices grown by e-beam evaporation have been investigated by using the combined three-axis magneto-optical Kerr effect, magnetotransport measurements, x-ray diffraction, Rutherford backscattering, transmission electron microscopy (TEM), and domain observation with scanning transmission electron microscope electron holography. Large-angle x-ray scattering data and TEM images indicate that the superlattices have fcc (111) orientation with polycrystalline grain sizes ranging from 10–14 nm. Small angle x-ray scattering and cross-section TEM images show that the superlattices have a well-defined layer structure, coherent grain-to-grain epitaxial growth, and interfacial roughness of ±0.2–0.4 nm. The correlations between the 90° magnetization and magnetoresistance oscillation curves suggest that the giant magnetoresistance in superlattices with imperfect interfaces results from the 90° orientation of domains within adjacent Co layers.