Surfactant-mediated control of the interface structure and solid-state properties of metallic multilayers

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We have investigated the surfactant effect of Bi on the homoepitaxial growth of Fe and the heteroepitaxial growth of Cr on Fe(100). Bi enhances the interlayer transport in the growth of Fe and Cr on Fe(100) by decreasing surface mobility, and layer-by-layer growth is facilitated. The dependence of the growth on Bi layer thickness suggests that there exists a suitable amount of Bi surfactant layer that enhances smoother layered growth. The surface segregation of Bi during growth is prominent, and we conclude that a large number of Bi atoms are present on the top of the surface.We have investigated the surfactant effect of Bi on the heteroepitaxial growth of Fe/Cr multilayers on Fe(100) surface by MBE and sputter deposition. Predeposition of a small amount of Bi surfactant enhances the layered growth of Fe/Cr multilayer. From these results, we concluded that Bi atoms acted as an effective surfactant in the Fe/Cr multilayer growth. The interface structures of Fe/Cr multilayer with Bi surfactant are sharper than that of multilayer without. Bi. The magnetoresistance ratio of the Fe/Cr multilayer with Bi was larger than that of the multilayer without Bi. These results imply that the sharpness of interfaces mediated by Bi surfactant can be related to the large GMR effect.We have also investigated the surfactant effect on the other system, Au/Co and Cu/Co, like as the Fe/Cr case. All of these results indicate that Bi surfactant enhances the interlayer transport in the growth of adatoms on metal substrates by decreasing surface mobility, and layer-by-layer growth is facilitated. These results mean that the surfactant would be effective in changing the interface structures of metallic multilayers, and that one can artificially control the magnetic property of multilayer using the surfactant species.