[1] Univ Wurzburg, Inst Phys, D-97074 Wurzburg, Germany
[2] Univ Wurzburg, Rontgen Res Ctr Complex Mat Syst, D-97074 Wurzburg, Germany
[3] Univ Kassel, Inst Phys, D-34132 Kassel, Germany
[4] Paul Scherrer Inst, Swiss Light Source, CH-5232 Villigen, Switzerland