1. Department of Physics, University of South Florida, 4202 East Fowler Ave., Tampa, Florida 33620, USA
2. National Institute of Standards and Technology, 325 Broadway, Boulder, Colarado 80305, USA
3. Chernivtsi Department, Frantsevich Institute of Material Sciences Problems, The National Academy of Sciences of Ukraine, 5, Iryna Vilde St., 58001 Chernivtsi, Ukraine
4. Physics Department, West Virginia University, Morgantown, West Virginia 26506-6315, USA
5. Materials Science Institute, University of Valencia, P.O. Box 2205, 46071 Valencia, Spain
6. Department of Physics, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA