1. School of Physics, Madurai Kamaraj University, Madurai 625021, India
2. Department of Physics/Centre for Materials Science and Nanotechnology, University of Oslo, P.O. Box 1048 Blindern, Oslo NO-0316, Norway
3. Department of Materials Science, National Research Nuclear University “MEPhI”, 31 Kashirskoe Sh., Moscow 115409, Russian Federation
4. Center for Materials Science and Nanotechnology, University of Oslo, Oslo 0371, Norway