[1] Tech Univ Ilmenau, Inst Phys, D-98693 Ilmenau, Germany
[2] Forschungszentrum Julich, Peter Grunberg Inst, D-52425 Julich, Germany
[3] Univ Cologne, Phys Inst 2, D-50923 Cologne, Germany
[4] Univ Konstanz, Fachbereich Phys, D-78457 Constance, Germany
[5] Wigner Res Ctr Phys, Inst Solid State Phys & Opt, Dept Theoret Solid State Phys, H-1121 Budapest, Hungary
[6] Univ Szeged, ELKH SZTE React Kinet & Surface Chem Res Grp, H-6720 Szeged, Hungary
[7] Budapest Univ Technol & Econ, Inst Phys, Dept Theoret Phys, H-1111 Budapest, Hungary