Experimentally, very small oxygen doses at Fe bilayer grown at Ag(001) change the magnetization direction from perpendicular to in-plane Phys. Rev. B 45 (1992) 3636. We attempt to analyze our previous semi-empirical tight-binding model Phys. Rev. B 63 (2001) 205427. For low oxygen coverage, we derive, however. only very small change of magnetic anisotropy energy. Nevertheless, we find indications of the tendency to surface-subsurface antiferromagnetic coupling induced by oxygen and changing markedly the magnetic anisotropy. Another possibility to explain the effect is a Preferred oxygen adsorption at specific sites leading to high-coverage regions at the surface. (C) 2002 Elsevier Science Ltd. All rights reserved. References: 17
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