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O: Oberflächenphysik

O 11: Epitaxy and growth I

O 11.6: Vortrag

Montag, 27. März 2006, 16:15–16:30, WIL A317

Large Film Stress of Fe, Co, and Ni monolayers on Ir(100) — •Z. Tian, C.S. Tian, D. Sander, and J. Kirschner — Max-Planck-Institut für Mikrostrukturphysik,

The mechanical stress of ferromagnetic monolayers(ML), which are deposited on different surface reconstructions of Ir(100) (1×1, 5×1-Hexagonal, 5×1-H) is measured with an optical bending beam technique during growth. Both Co and Ni show a large positive film stress of 17 and 15 GPa, respectively, during the initial stage of the growth(1-2ML). This stress corresponds to the calculated value based on continuum elasticity with a misfit strain of 8.8% for fcc-Co and 9.1% for Ni. The same magnitude of stress is measured irrespective of the surface reconstruction. A kink in the stress vs. coverage curve at 2 ML can be tentatively ascribed to the end of pseudomorphic growth. Ongoing deposition leads to a lower film stress, which relaxes to less than 2 GPa as the thickness increases above 10ML. The growth of Fe leads to a compressive film stress of -10 GPa in the thickness range 2-12 ML. This stress magnitude corresponds to the epitaxial misfit induced stress, if we take the lattice constant of bcc-Fe as a reference. We conclude that pseudomorphic growth of Fe ends around 12 ML. The results are discussed in view of film structure and morphology as obtained by in-situ LEED and MEED measurements and previous STM work[1]Lattice strain is often the decisive factor which determines the magnetic anisotropy of ferromagnetic monolayers (ML).

[1] L. Hammer, W. Meier, A. Schmidt and K. Heinz: Phys. Rev. B 67, 125422 (2003).