1. Department of Physics , N.M.S.S.Vellaichamy Nadar College , Madurai , Tamil Nadu 625019 , India
2. Materials Research Center , Coimbatore , Tamil Nadu 641045 , India
3. Department of Physics , Bharathiar University , Coimbatore , Tamil Nadu , India
4. Functional Materials Laboratory , Department of Physics , PSG Institute of Technology and Applied Research , Coimbatore , Tamil Nadu , India