MICROSTRUCTURAL CHARACTERIZATION OF CO/CU MULTILAYERS

A series of de magnetron-sputtered Co/Cu superlattices, with Co magnetic layers of similar to 10 Angstrom thickness and Cu spacer layer thicknesses in the range 10-400 Angstrom, has been characterized by high-resolution electron microscopy. The multilayer structure was found to be polycrystalline with individual columnar grains spanning several bilayers. The grain size increased for Cu spacer layers of greater thickness, with a grain size of at least 3-4 bilayer periods being typical for multilayers with the thickest Cu layers (100-400 Angstrom). In terms of the giant magnetoresistance (GMR) exhibited by these metallic superlattices, these observations mean that conduction electron scattering at grain boundaries can, to a first approximation, be ignored in models for GMR dependence on Cu layer thickness.