On the oxygen-driven magnetization reorientation in Fe(001) bilayer

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.