1. Department of Physics, Indian Institute of Technology (BHU), Varanasi 221005, India
2. Department of Chemistry, Banaras Hindu University, Varanasi 221005, India
3. Department of Physics, D.D.U. Gorakhpur University, Gorakhpur 273009, India
4. Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 2778581, Japan
5. Department of Physics, Institute of Science, Banaras Hindu University, Varanasi 221005, India
6. Department of Physics, School of Physical Sciences, Sikkim University, Gangtok, Sikkim 737102, India