INTERFACIAL-ROUGHNESS EFFECTS ON GIANT MAGNETORESISTANCE AND INTERLAYER COUPLING IN CO/CU SUPERLATTICES

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 fee (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 mm. The correlations between the 90 degrees magnetization and magnetoresistance oscillation curves suggest that the giant magnetoresistance in superlattices with imperfect interfaces results from the 90 degrees orientation of domains within adjacent Co layers.