CO THICKNESS DEPENDENCE OF THE MICROSTRUCTURE OF PT/CO MULTILAYERS

We have studied with high resolution electron microscopy the microstructure of polycrystalline Pt/Co multilayers with between 13- and 18-angstrom-thick Pt and Co thicknesses up to 20 angstrom. For thin Co (approximately 4 angstrom), Pt/Co multilayers had (111)-fcc texture normal to the substrate and a coherent lattice with interplanar spacing of approximately 2.2 angstrom, along the direction of chemical modulation. As the Co thickness increased, coherence was lost, and thicker Co layers had hcp structure with (002) texture, and the film surface roughness increased for less energetic deposition conditions. Coincident with a coherent structure (thin Co), Pt/Co multilayers have a large perpendicular magnetic anisotropy, important for their application in magnetic and magneto-optical devices.