1. Department of Physics, Mangalore Institute of Technology and Engineering, Moodbidri, Badaga Mijar -574225, India
2. Univ. Lille, CNRS, Centrale Lille, Univ. Polytechnique Hauts-de-France, UMR 8520-IEMN, Lille F-59000, France
3. Department of Physics, Mangalore University, Mangalagangothri, Mangalore- 574199, India