[1] Lalit Narayan Mithila Univ, Univ Dept Phys, Darbhanga 846004, India
[2] Samastipur Coll, Constituent Coll LNMU, Postgrad Dept Phys, Darbhanga 846004, Samastipur 848134, Bihar, India
[3] Jawaharlal Nehru Univ, Sch Phys Sci, New Delhi 110067, India
[4] Univ Delhi, ARSD Coll, Dept Phys, Expt Res Lab, New Delhi 110021, India
[5] Univ Nacl Autonoma Mexico, Ctr Nanociencias & Nanotecnol, CONACyT, Km 107 Carretera Tijuana-Ensenada AP 14,BC, Ensenada 22860, Mexico