1. Department of Physics, Karunya University, Coimbatore, India
2. Department of Physics, Sri Ramakrishna Mission Vidyalaya College of Arts & Science, Coimbatore, India
3. Department of Physics, Kongunadu College of Arts & Science, Coimbatore, India
4. School of Advanced Materials Engineering, Chonbuk National University, Jeonju-561 756, South Korea