1. LUNAM, IMMM, UMR 6283 CNRS,
Faculté des Sciences, 72085 Le Mans Cedex 09, France
2. ESRF, The European Synchrotron, 71 avenue des Martyrs, 38043 Grenoble Cedex 09, France
3. Department
of Physics, Norwegian University of Science and Technology (NTNU), Høgskoleringen 5, 7491 Trondheim, Norway