1. Department of Physics, Perunthalaivar Kamarajar Institute of Engineering and Technology, Karaikal-609 603, India.;
2. Research and Development Centre, BharathiarUniversity, Coimbatore -641 046, India.;
3. School of Physics, Bharathidasan University, Tiruchirappalli, 620024, India.;
4. Division of Physics, School of Advanced Science, VIT Chennai, Chennai, 600 127, India.