1. Department of Physics, Chemistry and Biology, Linköping University, SE-581 83 Linköping, Sweden
2. GLO AB, Scheelevägen 22, SE-22363 Lund, Sweden
3. Solid State Physics, Lund University, Box 118, SE-22100 Lund, Sweden
4. TokyoUniversity of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan