1. Department of Mechanical Engineering, University of Rochester 1 , Rochester, New York 14627, USA
2. School of Physics, Universidad Industrial de Santander 2 , Carrera 27 Calle 9, 680002 Bucaramanga, Colombia
3. Department of Physics and Astronomy, West Virginia University 3 , Morgantown, West Virginia 26505-6315, USA
4. Materials Science Program, University of Rochester 4 , Rochester, New York 14627, USA