1. Rzhanov Institute of Semiconductor Physics, Novosibirsk 630090, Russia
2. Novosibirsk State University, Novosibirsk 630090, Russia
3. Experimental and Applied Physics, University of Regensburg, D-93040 Regensburg, Germany
4. LNCMI, UPR 3228, CNRS-INSA-UJF-UPS, BP166, F-38042 Grenoble cedex 9, France
5. Institut NEEL, CNRS-UJF UPR2940, 25 rue des Martyrs, BP166, F-38042 Grenoble cedex 9, France
6. Institut Universitaire de France and Institut National des Sciences Appliques, F-31077 Toulouse Cedex 4, France