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Y. JYOKO, S. KASHIWABARA AND Y. HAYASHI Kyushu University, Faculty of Engineering, Fukuoka 812, Japan

ABSTRACT Reflection electron microscopy (REM) studies of Co electrodeposition on Pt(111) singlecrystal surfaces under potential control have revealed a heteroepitaxial and simultaneous multinuclear multilayer growth in a range from several up to some ten monolayer coverages at room temperature. This growth process has been dependent upon the crystallization overpotential during electrodeposition. REM observations have also suggested the formation of an ordered CoPt 3 alloy at the interface between the Pt/Co ultrathin bilayers grown epitaxially on Pt(111) surfaces. Auger and photoelectron spectroscopy experiments on the Pt/Co/Pt(111) system have confirmed a limited interdiffusion or interfacial alloying below the Pt overlayer leading to an induced magnetic moment on the Pt atoms. The Pt/Co interface exhibits electronic interface states of mainly Pt-5d character. Cross-sectional transmission electron microscopy (TEM) observations have provided the first direct experimental evidence for composition modulation across successive layers in a Pt/Co nanometer-multilayered structure prepared by electrodeposition.

INTRODUCTION Magnetic and metallic multilayers are of intense interest currently for their unusual magnetic properties and potential applicability to electromagnetic devices. In particular, perpendicular magnetic anisotropy with square hysteresis loops, which has been observed for Pt/Co multilayers when the Co layer thickness is less than a few atomic layers, has attracted considerable attention as magneto-optical storage media [1]. Most of these multilayers have been fabricated by molecular beam epitaxy (MBE) or sputtering, which are suitable for the controlled preparation of individual layers on the order of monatomic layers. Electrodeposition from aqueous solutions may also be a promising candidate for this purpose. It must be emphasized that the electrodeposition process does not require a vacuum system, and hence is more suitable for producing multilayers with a large area in an arbitrary shape at a cost lower than vapor-phase deposition techniques, and that it can be carried out at room temperature. The latter advantage may be important for systems in which undesirable interdiffusion between the adjacent layers may readily occur. We have focused our attention on the feasibility of electrodeposition to produce magnetic multilayers with predesignable, variable, and controllable composition and structure on an atomic scale. Very few papers directly addressing this subject, however, have been published so far, except for recently prepared Cu/Ni or Cu/Co-Ni-Cu compositionally modulated multilayered alloys [2,3] and Ni/Ni-P multilayered thin films [4]. We have previously reported [5] REM observations of the initial stages of Co electrodeposition on a Pt(11) surface controlling crystallization overpotential which corresponds to the supersaturation in gas-phase deposition. In this paper we present the results of RE