[1] Louisiana State Univ, Dept Phys & Astron, Baton Rouge, LA 70803 USA
[2] Indian Inst Technol BHU, Sch Mat Sci & Technol, Varanasi 221005, India
[3] Indian Inst Technol, Dept Elect Engn, Mumbai 400076, India
[4] Indian Inst Technol Kanpur, Dept Earth Sci, Kanpur 208016, India
[5] Motilal Nehru Natl Inst Technol Allahabad, Dept Phys, Prayagraj 211004, India