1. Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560012, India, Department of Physics, Goa University, Goa 403206, India, Institute of Scientific and Industrial Research, Osaka University, Mihoga-oka 8-1, Ibaraki, Osaka 567-0047, Japan, Department of Material Science, Faculty of Science, Osaka City University, Sugimoto 3-3-138, Sumiyoshi-ku, Osaka 558-8585, Japan, and Materials Research Centre, Indian Institute of Science, Bangalore-560012, India