1. Department of Physics, Institute of Science, Banaras Hindu University, Varanasi 221005, India
2. Central Instrument Facility, Indian Institute of Technology (Banaras Hindu University), Varanasi 221005, India
3. CSIR-National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi 110012, India
4. Department of Physics, Indian Institute of Technology (Banaras Hindu University), Varanasi 221005, India