[1] BESSY, D-12489 Berlin, Germany
[2] Uppsala Univ, Dept Phys, S-75121 Uppsala, Sweden
[3] Div Theoret, Los Alamos Natl Lab, Los Alamos, NM 87545 USA
[4] Kyoto Univ, Dept Mat Sci & Engn, Kyoto 6068501, Japan
[5] Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden