[1] Bhabha Atom Res Ctr, Tech Phys Div, Mumbai 400085, Maharashtra, India
[2] Max Planck Inst Festkorperforsch, D-70569 Stuttgart, Germany
[3] Bhabha Atom Res Ctr, Div Radiochem, Mumbai 400085, Maharashtra, India
[4] Indian Inst Technol, Dept Phys & Meteorol, Kharagpur 721302, W Bengal, India
[5] Indian Assoc Cultivat Sci, Dept Solid State Phys, Kolkata 700032, India
[6] Indian Assoc Cultivat Sci, Dept Mat Sci, Kolkata 700032, India