1. Department of Physics, Adamas University, Barasat - Barrackpore Road, Kolkata 700 126, India
2. Department of Physics, Vidyasagar Evening College, 39 Sankar Ghosh Lane, Kolkata 700 006, India
3. Department of Physics, University of Calcutta, 92 A P C Road, Kolkata 700 009, India
4. Department of Physics, Raiganj University, Uttar Dinajpur, West Bengal 733 134, India
5. Department of Low Temperature Physics and Superconductivity, Physics Faculty, M.V. Lomonosov Moscow State University, 119991 Moscow, Russia
6. Surface and Nanoscience Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, India
7. Physical Metallurgy Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, India
8. Center for Research in Nanoscience and Nanotechnology, University of Calcutta, JD-2, Sector-III, Saltlake, Kolkata 700 106, India