1. Department of Physics, Faculty of Physics, University of Isfahan, Isfahan 81746-73441, Iran
2. Instituto Regional de Investigación Científica Aplicada (IRICA) and Departamento de Física Aplicada, Universidad de Castilla-La Mancha, 13071 Ciudad Real, Spain
3. Faculty of Physics and CENIDE, Universität Duisburg-Essen, 47048 Duisburg, Germany
4. Physics Department, North Carolina State University, Raleigh, NC 27606, USA
5. Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27606, USA
6. Department of Electrical and Computer Engineering, North Carolina State University, Raleigh, NC 27606, USA