1. 1Department of Physics, Andhra Loyola College, Vijayawada-520008, India 2Department of Physics, Acharya Nagarjuna University, Nagarjuna Nagar-522510, India
2. Department of Physics, Andhra Loyola College, Vijayawada-520008, India
3. Department of Physics, National Institute of Technology, Warangal-506004, India
4. Department of Physics, Maris Stella College, Vijayawada-520008, India