[1] Osmania Univ, Univ Coll Sci, Dept Phys, Hyderabad 500004, India
[2] Mahatma Gandhi Univ, Univ Coll Sci, Dept Phys, Nalgonda 508254, India
[3] St Marys Grp Inst, Dept Phys, Deshmukhi 508116, Yadadri Bhongir, India
[4] Osmania Univ, Univ Post Grad Coll, Dept Phys, Secunderabad 500003, India