1. Institute of Physics, Nicolaus Copernicus University in Torun, Torun 87-100, Poland
2. Department of Electrical Engineering, Indian Institute of Technology, Kanpur 208016, India
3. Institut für Physik, Johannes Gutenberg Universität Mainz, D-55099 Mainz, Germany
4. Department of Physics, Indian Institute of Technology, Kanpur 208016, India
5. Department of Materials Science and Engineering, Indian Institute of Technology, Kanpur 208016, India