IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Surface Science Thursday Sessions
       Session SS3-ThP

Paper SS3-ThP7
CO Adsorption on the c(2x2)-Mn/Cu(100) Surface Alloy: Magnetically Driven Restructuring

Thursday, November 1, 2001, 5:30 pm, Room 134/135

Session: Surface Reactions Poster Session
Presenter: M. Grüne, Universität Bonn, Germany
Authors: M. Grüne, Universität Bonn, Germany
G. Boishin, Universität Linz, Austria
C. Becker, Universität Bonn, Germany
J. Breitbach, Universität Bonn, Germany
A. Frey, Universität Bonn, Germany
T. Pelster, Universität Bonn, Germany
K. Wandelt, Universität Bonn, Germany
Correspondent: Click to Email
The c(2x2)-Mn/Cu(100) surface alloy is stabilized by the large magnetic moment of the Mn atoms yielding a substantial exchange energy.@footnote 1@ We have investigated the adsorption of CO on this alloy at 100 K by means of HREELS, UPS, LEED, and work function measurements. CO chemisorption passes through two subsequent stages. In no stage a CO-induced superstructure LEED pattern is seen. Initial adsorption of mainly side-on-CO, accompanied by adsorption at defects, leaves the substrate order intact. Subsequent adsorption of CO ontop Mn irreversibly destroys the long-range order of the substrate. This takes place by lateral interdiffusion, as can be shown by the application of UPS symmetry selection rules. We propose that the loss of the translational symmetry is related to a suppression of the local magnetic moment by ontop-CO adsorption. The reduction of the mnagnetic energy contribution causes a lifting of the energetic exclusion of Mn nearest neighbours, leading to a considerable entropy gain by lateral intermixing. @FootnoteText@ @footnote 1@see e.g.: M. Wuttig, Y. Gauthier, S. Blügel, Phys. Rev. Lett. 23 (1993) 3619-3622.