1. Department of Materials Science and Engineering, University of Rajshahi, Rajshahi 6205, Bangladesh
2. Department of Physics, University of Rajshahi, Rajshahi 6205, Bangladesh
3. International Islamic University Chittagong, Kumira, Chittagong 4318, Bangladesh
4. Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8573, Japan