1. Experimentelle Physik III, Physikalisches Institut and Wilhelm Conrad, Röntgen-Research Centre for Complex Material Systems; Universität WürzburgAm Hubland; D-97074 Würzburg Germany
2. Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons and Peter Grünberg Institute 5; Forschungszentrum Jülich D-52425 Jülich Germany
3. Institute of Physics, Polish Academy of Sciences; Al. Lotników 32/46 02-668 Warsaw Poland